Monitoring health of heat transfer fluids for electric systems

ABSTRACT

A method of operating a heat transfer system includes circulating a heat transfer fluid through a heat transfer circuit in fluid communication with an electric system, and obtaining real-time measurements of fluid properties of the heat transfer fluid. A dimensional effectiveness factor for the heat transfer fluid (DEFfluid) is calculated based on the fluid properties and for a selected pump and a selected dominant flow regime within the heat transfer circuit, and a dimensional effectiveness factor for a reference fluid (DEFreference) is calculated for the selected pump and the selected dominant flow regime within the heat transfer circuit. A normalized effectiveness factor (NEFfluid) of the heat transfer fluid is then obtained, whereby a health of the heat transfer fluid is obtained. If the NEFfluid is below a predetermined threshold, the health will be considered deteriorated, and if the NEFfluid is above the predetermined threshold, the health will be considered viable.

FIELD OF THE INVENTION

The present disclosure is related to heat transfer fluids for use inelectrical systems and, more particularly, to improving performance ofheat transfer systems of electric systems by determining the real-timehealth of a heat transfer fluid.

BACKGROUND OF THE INVENTION

Heat transfer systems are incorporated into many types of electricsystems to help remove generated heat and thereby regulate prolongedoperation of the electric systems. Electric vehicles are one type ofelectric system that requires an efficient heat transfer system toremove heat generated through operation. Heat transfer systems forelectric vehicles typically use aqueous heat transfer fluids(alternately referred to as “coolants”) that indirectly remove generatedheat from particular electrical components, such as batteries andelectric motors. As electric vehicle technology evolves to comprehendlonger battery ranges, shorter recharging times, and higher vehiclepower, there are benefits associated with direct cooling of electricalcomponents, which is not possible with aqueous heat transfer fluids.

The use of non-aqueous, dielectric heat transfer fluids, such ashydrocarbon-based fluids, can reduce the possibility of safety issuesassociated with the electrical conductivity of water, including thepotential risk of hydrogen formation and release. Based on its lowelectrical conductivity, hydrocarbon-based heat transfer fluids providebenefits in the evolving electric vehicle application with respect tosafety and direct cooling of surfaces of hot electrical components.

In many electric vehicle applications, the performance of a heattransfer fluid is governed both by its ability to remove heat fromelectrical components and by the amount of power required to circulatethe heat transfer fluid within a heat transfer circuit. An ideallysuited heat transfer fluid will maximize heat removal and requireminimum power to circulate the fluid.

Depending on the design of the electric vehicle, the specific fluidproperties of a heat transfer fluid that will govern its overallperformance will differ. For instance, in an electric vehicle designwhere there is a large surface area across which heat is to be removed,and a large surface area across which heat is subsequently removed fromthe heat transfer fluid to lower its temperature before recirculation,the heat capacity of the heat transfer fluid will dominate indetermining the amount of heat flow from the hot components to the heattransfer fluid. In other electric vehicle designs, fluid properties suchas viscosity, density, and thermal conductivity can also play key rolesin determining the heat flow. In each case, the fluid properties of theheat transfer fluid can also be important in determining the amount ofpower required to circulate the heat transfer fluid.

While there has been much advancement and understanding of the expectedlifetime and degradation pathways for oils in internal combustionengines, there is minimal experience and development in understandingand predicting the health of heat transfer fluids in electric systems,such as electric vehicles.

SUMMARY OF DISCLOSURE

Various details of the present disclosure are hereinafter summarized toprovide a basic understanding. This summary is not an extensive overviewof the disclosure and is neither intended to identify certain elementsof the disclosure, nor to delineate the scope thereof. Rather, theprimary purpose of this summary is to present some concepts of thedisclosure in a simplified form prior to the more detailed descriptionthat is presented hereinafter.

In one or more aspects, a method of operating a heat transfer system isdisclosed and includes, circulating a non-aqueous, dielectric heattransfer fluid through a heat transfer circuit in fluid communicationwith an electric system, the heat transfer circuit including a pump, aconduit, and a heat exchanger, obtaining real-time measurements of fluidproperties of the heat transfer fluid within the heat transfer circuit,the fluid properties being selected from the group consisting of density(ρ), specific heat (c_(p)), dynamic viscosity (μ), and thermalconductivity (k), calculating a dimensional effectiveness factor for theheat transfer fluid (DEF_(fluid)) based on the real-time fluidproperties and for a selected pump and a selected dominant flow regimewithin the heat transfer circuit, calculating a dimensionaleffectiveness factor for a reference fluid (DEF_(reference)) and for theselected pump and the selected dominant flow regime within the heattransfer circuit, determining a normalized effectiveness factor(NEF_(fluid)) of the heat transfer fluid from the following equation:

${{NEF_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}},$

and determining a health of the heat transfer fluid based on theNEF_(fluid), wherein if the NEF_(fluid) is below a predeterminedthreshold, the health will be considered deteriorated, and wherein ifthe NEF_(fluid) is above the predetermined threshold, the health will beconsidered viable.

In one or more additional aspects, another method of operating a heattransfer system includes circulating a non-aqueous, dielectric heattransfer fluid through a heat transfer circuit in fluid communicationwith an electric system, the heat transfer circuit including a pump, aconduit, and a heat exchanger, obtaining real-time measurements of fluidproperties of the heat transfer fluid within the heat transfer circuit,the fluid properties being selected from the group consisting of density(ρ), specific heat (c_(p)), dynamic viscosity (μ), and thermalconductivity (k), calculating a dimensional effectiveness factor for theheat transfer fluid (DEF_(fluid)) based on the real-time fluidproperties and for a selected pump and a selected dominant flow regimewithin the heat transfer circuit, calculating a dimensionaleffectiveness factor for a reference fluid (DEF_(reference)) and for theselected pump and the selected dominant flow regime within the heattransfer circuit, determining a normalized effectiveness factor(NEF_(fluid)) of the heat transfer fluid from the following equation:

${{NEF_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}},$

determining a health of the heat transfer fluid based on theNEF_(fluid), wherein if the NEF_(fluid) is below a predeterminedthreshold, the health will be considered deteriorated, and wherein ifthe NEF_(fluid) is above the predetermined threshold, the health will beconsidered viable, monitoring a temperature of the electric system, anddetermining that the electric system has a hardware issue if thetemperature exceeds a predetermined temperature limit and the health ofthe heat transfer fluid is viable.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, withoutdeparting from the scope of this disclosure.

FIG. 1 is a schematic diagram of an example heat transfer system thatmay incorporate the principles of the present disclosure.

FIG. 2 illustrates an example embodiment of the computer system of FIG.1 .

DETAILED DESCRIPTION

The present disclosure is related to heat transfer fluids for use inelectrical systems and, more particularly, to improving performance ofheat transfer systems of electric systems by determining the real-timehealth of a heat transfer fluid

All percentages in describing heat transfer fluids herein are by weightunless specified otherwise. “Wt.%” means percent by weight.

“Electric system, “electric device,” “electrical system, “electricaldevice,” and any variant thereof, refers to any system, device, orapparatus primarily powered or operated through electrical means andrequiring a heat transfer system to remove generated heat for prolongedoperation. Example electric systems include, but are not limited to, anelectric vehicle, power electronics included in an electric vehicle(e.g., “on-board” electronics), an electric motor, a battery, arechargeable battery system, a charging station, electronic equipment, acomputer, a server bank (or farm), a data center, or any combinationthereof.

“Electric vehicle,” and any variant thereof, refers to all-electric andfully electric vehicles, and hybrid and hybrid electric vehicles, whichmay have any of a variety of parallel or series drivetrainconfigurations, alone or in combination, and includes the mechanical andelectrical systems, subsystems, and components having gears used in thevehicles. These mechanical and electrical systems, subsystems andcomponents having gears can include, for example, electrical vehiclepowertrains, powertrain components, drivetrain components, kineticenergy recovery systems (KERS), energy regenerative systems, and thelike. The terms electric vehicle and hybrid vehicle may be usedinterchangeably. Moreover, the term “electric vehicle” is not limited toland-bound vehicles (e.g., automobiles), but is also intended toencompass any type of vehicle that is fully or partially poweredelectrically and includes aviation vehicles (e.g., airplanes, drones,spacecraft, etc.) and nautical vehicles (e.g., any type of water craft,hovercraft, etc.). “Electric vehicle” can also refer to manually-drivenor autonomous vehicles, or any hybrid thereof.

It has been found that the removal of heat from electrical components ordevices such as batteries, on-board power electronics, super-fastcharging systems, and electric motors during electric vehicle operationcan be done using non-aqueous heat transfer fluids, which directlyremove heat from the hot surfaces. Non-aqueous heat transfer fluids,such as the hydrocarbon-based heat transfer fluids mentioned in thisdisclosure, can provide benefits in the evolving electric vehicletechnology space with respect to both direct cooling of hot componentsurfaces and safety based on the low electrical conductivity of thenon-aqueous heat transfer fluids.

In electric vehicle applications, as indicated above, the performance ofa heat transfer fluid is governed both by its ability to remove heatfrom hot surfaces and by the amount of power required to circulate theheat transfer fluid through the heat transfer circuit. Ideally, aselected heat transfer fluid will maximize heat removal and requireminimum power to circulate the fluid through a heat transfer circuit.

The effectiveness of a heat transfer fluid in a given electric vehicledesign can be defined as the ratio of heat flow (HF) to the power tocirculate the heat transfer fluid (PC). An electric vehicle heattransfer fluid with a higher effectiveness will be able to remove moreheat from hot surfaces per amount of power required to circulate thefluid, and this will provide significant benefits in terms of maximizingelectric vehicle battery range and/or optimizing the design of thecooling system in the vehicle. By evaluating the electric vehicle designparameters in conjunction with the effectiveness of the heat transferfluid in particular vehicle applications, it has been determined how HFand PC are each impacted by the fluid properties of the heat transferfluid, e.g., density (ρ), viscosity (μ), heat capacity or specific heat(c_(p)), and thermal conductivity (k). This has led to theidentification of a unique combination of fluid properties, referred toherein as the normalized effectiveness factor (NEF_(fluid)), thatmaximize the effectiveness of a heat transfer fluid for the electricvehicle designs described herein.

Unexpectedly, the normalized effectiveness factor (NEF_(fluid)) differsfrom the combination of fluid properties commonly proposed in theindustry as generally applying with respect to heat transfer of liquidcoolants, and known as the Mouromtseff equation (or number). As aresult, for heat transfer fluids with properties yielding higherNEF_(fluid) values than comparative materials with lower NEF_(fluid)values, the overall performance of the electric vehicle cooling systemcan be improved and optimized. In some cases, for example, improvementin performance of a heat transfer system is obtained by using a heattransfer fluid having an NEF_(fluid) equal to or greater than 1. In atleast one embodiment, NEF_(fluid)=1 may correspond to a fresh heattransfer fluid, and fractional values for the degrading heat transferfluid during operation are a direct indication of its decreased utilityor degree of degradation. In such embodiments, fluid replacement mightbe triggered when the value of NEF_(fluid) drops below a user specifiedvalue (fraction).

The Mouromtseff equation was developed as a quick and convenient methodfor comparing the impact of fluid properties on the resulting heattransfer coefficient. While the use of the Mouromtseff equation providesa convenient method for quickly comparing fluids, its use has a numberof shortcomings, for example, with respect to flow rate, dimensionality,and dominant heat conveyance mechanism.

With respect to flow rate, in eliminating all of the variables from heattransfer correlations except those having to do with fluid physicalproperties, the traditional Mouromtseff equation derivation ignores anyimpact that the fluid properties may have on the fluid circulation rate.In particular, if a centrifugal pump is being used to circulate the heattransfer fluid, the fluid properties of the heat transfer fluid willimpact the circulation rate in a specific way and, therefore, impact theresulting local fluid velocity. Thus, a variable is typicallyeliminated, when it depends itself on the fluid properties, and thisdependency should be included in any fluid comparison.

With respect to dimensionality, the fluid property variables used in thetraditional Mouromtseff equation have units. This means that unlike theNusselt (Nu), Reynolds (Re), and Prandlt (Pr) numbers, the resultingMouromtseff equation is not dimensionless; however, the appropriateunits are frequently not reported in the literature. Therefore, any twodifferent practitioners who calculate a Mouromtseff equation for thesame fluid may produce different numbers, depending on, for example, ifone uses Si units, and the other uses imperial units.

With respect to the dominant heat conveyance mechanism, use of theMouromtseff equation implies that heat removal in the physical situationin which the fluid is to be used is dominated by localized heat transferwith the fluid. In some situations, however, heat conveyance by thecirculating heat transfer fluid may dominate, such as in scenarios wherelarge heat transfer areas exist at the element to be cooled and the heatrejection site. In such situations, the actual mechanism of local heattransfer, and therefore fluid property impacts on the local heattransfer, become irrelevant. In these applications, while theMouromtseff equation may be indicating something about the heat transferfluid, what it is indicating may be irrelevant to the fluid performanceas a heat transfer fluid.

Power is required to circulate the heat transfer fluid. For some heattransfer applications where this power is independently supplied, thismay not be an issue. However particular in mobility applications, thispower to circulate the fluid is often provided by the same power sourcethat provides the power for the mobility. For example, in an electricvehicle, the battery provides the power for vehicle motion, and thepower for circulating the heat transfer fluid. A similar situationoccurs in aeronautical and aerospace applications. In such situations,when comparing fluids for heat transfer service, one needs to considerboth how the fluid properties impact heat transfer, and how the fluidproperties impact the power required to circulate the fluid.

The power required to circulate the heat transfer fluid is simply theproduct of the fluid volumetric flowrate and the pressure drop throughthe circulating circuit. This does not include any inefficiencies of thespecific pump performing this circulating power, and is assumed to bedelivered by an ideal pump. The impact of fluid properties on both thevolumetric flowrate of the circulating fluid, and the pressure dropthrough the circuit will be dependent on what flow regime dominatespressure drop in that circuit. In other words, the presence of laminar,transitional, or turbulent flow regimes in the heat transfer circuitwill lead to different relationships.

Equally, the specific type of pump being used to circulate the heattransfer fluid will have an impact. For an ideal positive displacementpump, for example, the volumetric flowrate will always be constant,regardless of fluid properties, but the resulting pressure drop will beimpacted by the fluid properties of the heat transfer fluid. In thatsituation, the localized heat transfer dominance and heat conveyancedominance will both not change due to flowrate, but the pumping powerwill still vary for different fluids. On the contrary, if a constantpressure pump were to be used (i.e., a pump circulation system where thedelivery pressure was constant, regardless of flowrate), the flowratewould change with physical properties, as would therefore the powerrequired to circulate the fluid. For a centrifugal pump, both thedelivered pressure and the volumetric flow could change with differentheat transfer fluids.

As described herein, a new type of heat transfer fluid effectivenessfactor can be used to consider both the performance of a heat transferfluid as a heat transfer medium, and the power required to circulate theheat transfer fluid through a heat transfer circuit. This effectivenessfactor will depend on the specific cooling application, depending onwhether heat transfer within the electrical component to be cooleddominates or whether heat conveyance by the circulating heat transferfluid dominates (typically because of relatively large heat transferareas, or because low circulation rates are used). This effectivenessfactor is referred to herein as a dimensional effectiveness factor(DEF_(fluid)) because it will have the same units deficiency as theMouromtseff equation. It will have units, making its specific valuedependent on the units used for the specific properties.

When heat conveyance is the dominant mode controlling performance of theheat transfer fluid in a cooling application, the dependencies on fluidproperties for the specified fluid circulation flow regimes and pumptypes for the dimensional effectiveness factor (DEF_(fluid)) are givenin Table 1:

TABLE 1 Heat Transfer Fluid and Reference Fluid Selected Heat TransferCircuit Flow Regime Transitional Turbulent Selected Pump Laminar(Blasius) (Rough Pipe) Positive Displacement ρ¹ c_(p) ¹ μ⁻¹ ρ^(0.25)c_(p) ¹ μ^(−0.25) c_(p) ¹ Pump Centrifugal Pump ρ^(0.19) c_(p) ¹μ^(−0.19) ρ^(0.04) c_(p) ¹ μ^(−0.04) c_(p) ¹

In Table 1, the specifics of the heat transfer are not relevant, sincethey do not control the heat transfer fluid's heat transfer performance.Thus, the heat transfer fluid could be flowing through tubes, or overflat plates, or being sprayed as a jet, or any other fluid contactmechanism, and because the heat conveyance is dominant, the applicabledimensional effectiveness factor (DEF_(fluid)) equation from Table 1would apply. Since the localized heat transfer mechanism is notimportant, it can be seen that the thermal conductivity (k) of the heattransfer fluid does not appear in Table 1 for any of the cases.

In cases when localized heat transfer is instead the dominant modecontrolling performance of the heat transfer fluid in a coolingapplication, thermal conductivity (k) would then be taken intoconsideration. Moreover, the dependencies on the fluid properties forthe specified fluid circulation flow regimes and pump types for thedimensional effectiveness factor (DEF_(fluid)) would be different fromthose shown in Table 1. Accordingly, the dimensional effectivenessfactor (DEF_(fluid)) equations given in Table 1 are merely provided forillustrative purposes based in applications where heat conveyance is thedominant mechanism controlling performance of the heat transfer fluid.Thus, the equations should not be considered particularly limiting tothe principles of the present disclosure, but instead merely provides anexample. In other examples, equations may be provided where local heattransfer through tube-like geometry is the dominant mechanismcontrolling performance of the cooling fluid, where local heat transferby flow over a flat plate is the dominant mechanism controllingperformance of the cooling fluid, or where local heat transfer by jetflow onto a flat plate is the dominant mechanism controlling performanceof the cooling fluid in an application.

To overcome the issue of the dependence of the dimensional effectivenessfactor (DEF_(fluid)) on the units system being used, the normalizedeffectiveness factor (NEF_(fluid)) initially introduced above is used.The normalized effectiveness factor (NEF_(fluid)) is given by thefollowing equation:

${{NE}F_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}$

where DEF_(fluid) is the dimensional effectiveness factor for the heattransfer fluid that is determined based on an equation designated inTable 1 (or an equation in another table corresponding to localized heattransfer dominant applications) for a selected pump and a selected heattransfer circuit dominant flow regime, and DEF_(reference) is adimensional effectiveness factor for a reference fluid that isdetermined using the same equation designated in Table 1 for DEF_(fluid)and for the same selected pump and the same selected heat transfercircuit dominant flow regime. Both DEF_(fluid) and DEF_(reference) aredetermined at the same predetermined temperature, and matching units foreach property are used in each equation.

The predetermined temperature for determining DEF_(fluid) andDEF_(reference) can vary over a wide range. For example, thepredetermined temperature can be between about −40° C. and about 175°C., or between about −25° C. and about 170° C., or between about −10° C.and about 165° C., or between about 0° C. and about 160° C., or betweenabout 10° C. and about 155° C., or between about 25° C. and about 150°C., or between about 25° C. and about 125° C., or between about 30° C.and about 120° C., or between about 35° C. and about 115° C., or betweenabout 35° C. and about 105° C., or between about 35° C. and about 95°C., or between about 35° C. and about 85° C. Preferred predeterminedtemperatures for determining DEF_(fluid) and DEF_(reference) include 40°C. or 80° C.

Example reference fluids that can be used in accordance with the presentdisclosure include, for example, conventional fluids known in the artsuch as biphenyl 26.5%+diphenyl oxide 73.5% (Dowtherm A), siloxane(>95%, KV100 16.6 cSt) (Duratherm S), organosilicate ester (>90%, KV1000.93 cSt) (Coolanol 20), organosilicate ester (>90%, KV100 1.6 cSt)(Coolanol 25R), perfluoro fluid C5-C8 (KV25 2.2 cSt) (Fluorinert FC-40),3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane(>99%) (Novec 7500), and the like. In other embodiments, the referencefluid may be the same as the heat transfer fluid, but without anydegradation of its fluid properties; i.e., fresh or new heat transferfluid. More specifically, in one or more aspects, the reference fluidmay be the same as and otherwise exhibit the same properties as the heattransfer fluid in a fresh or unused state. In such aspects, and prior tooperational use of the heat transfer fluid, NEF_(fluid) would equal 1since the DEF_(fluid) would essentially be divided by itself.Consequently, and as will be discussed in more detail below, anysubsequent deterioration of the heat transfer fluid through operationwith time would result in NEF_(fluid) of some fractional value as thevalue of DEF_(fluid) decreases.

The fluid properties of a given reference fluid DEF_(reference) arereadily available in the literature and, provided consistent units areused for evaluation of the DEF_(fluid) and DEF_(reference), thenormalized effectiveness factor (NEF_(fluid)) will be dimensionless,thus eliminating one of the shortcomings of the DEF_(fluid) and suchmeasures as the Mouromtseff equation.

For any specific cooling application, the appropriate density (ρ),specific heat (c_(p)), dynamic viscosity (μ), and thermal conductivity(k) properties can be determined, then those properties can be used tocalculate the DEF_(fluid) and the DEF_(reference), from which theNEF_(fluid) can be determined.

The fluid properties that the normalized effectiveness factor(NEF_(fluid)) depends on are all temperature dependent. For purposes ofthis disclosure, the properties should be evaluated at the averagetemperature in the element to be cooled. For the use of the equations todefine a fluid, a temperature of 40° C. or 80° C. can be used, howeverany other temperature can be used, provided that the same temperature isused for both the heat transfer fluid being evaluated, and for theproperties of the reference fluid.

The normalized effectiveness factor (NEF_(fluid)) equation providedabove has a number of benefits as compared to using the Mouromtseffequation for evaluating fluids for heat transfer applications. Theprimary benefit of the NEF_(fluid) equation is the consideration of thepower required to circulate the heat transfer fluid when evaluating thefluid's potential heat transfer performance. The NEF_(fluid) equationcan be thought of as providing a measure of the heat transfer potentialper unit of fluid circulating energy. For applications where the powersupply is shared between circulating the heat transfer fluid andproviding power for other uses, minimization of the power required forcirculation will maximize the power available for other purposes.

Alternately, if utilized during the design process, a similar rangecould be produced using a smaller battery. Alternately, the vehicledesigner could utilize the added power to provide additional poweredfeatures on the vehicle. Similarly, in an aeronautical application, thereduced circulating power could lead to improved fuel economy, anincrease range, or additional features being installed on the aircraft.In an aerospace application, power is typically provided via solarcollectors. This limitation on the available power places a greateremphasis on power management and use of the normalized effectivenessfactor (NEF_(fluid)) equation provides a means of obtaining the maximumamount of heat transfer for the limited amount of available circulatingpower.

The traditional derivation of the Mouromtseff equation ignores theimpact of fluid properties on the velocity during the simplification ofthe heat transfer correlations. While this is less important forapplications where a positive displacement is used to circulate thefluid, it is important for other pump types. The normalizedeffectiveness factor (NEF_(fluid)) equation approach ensures that thefluid properties are fully encompassed in the analysis.

Historic use of the Mouromtseff equation leads to use of numbers thathave units. Comparison of values with different units is notstraightforward. Because the normalized effectiveness factor(NEF_(fluid)) equation is unitless, it provides a convenient means ofcomparison of values from different sources.

Use of the Mouromtseff equation approach to fluid evaluation impliesthat the local heat transfer process is the dominant mechanism, whichdictates the fluids heat transfer performance. This is not always thecase. Fluid evaluation needs to be made based on an understanding of thedominant mechanism, which dictates heat transfer performance. Thenormalized effectiveness factor (NEF_(fluid)) equation approach providesdifferent options for different applications. This provides a morerigorous and correct method for fluid evaluation.

The heat transfer fluids mentioned herein exhibit fluid properties(e.g., density (ρ), specific heat (c_(p)), and dynamic viscosity (μ))for imparting satisfactory heat transfer performance in specificelectric systems. In addition, the heat transfer fluids mentioned hereincan possess other properties that are beneficial for their use inspecific devices. Such other properties include, for example, thermalconductivity (k) and flash point. Having a heat transfer fluid with ahigher thermal conductivity (k) can be beneficial because it increasesthe rate of heat transfer, and having a fluid with a higher flash pointcan be beneficial because it reduces flammability. Further, heattransfer fluids having properties that impart electrical compatibility,and compatibility with materials in specific electric systems anddevices, can be beneficial in specific electric devices.

As used herein, density (ρ) is determined in accordance with ASTM D8085or D4052, specific heat (c_(p)) is determined by ASTM E1269, and dynamicviscosity (μ) is determined by ASTM D8085 or derived from ASTM D445 andASTM D4052.

In an embodiment, at a temperature of 40° C., the heat transfer fluidsmentioned herein have a density (ρ) from about 0.25 g/mL to about 1.75g/mL, or from about 0.30 g/mL to about 1.70 g/mL, or from about 0.35g/mL to about 1.65 g/mL, or from about 0.40 g/mL to about 1.60 g/mL, orfrom about 0.45 g/mL to about 1.55 g/mL.

In another embodiment, at a temperature of 80° C., the heat transferfluids mentioned herein have a density (ρ) from about 0.25 g/mL to about1.75 g/mL, or from about 0.30 g/mL to about 1.70 g/mL, or from about0.35 g/mL to about 1.65 g/mL, or from about 0.40 g/mL to about 1.60g/mL, or from about 0.45 g/mL to about 1.55 g/mL.

In an embodiment, at a temperature of 40° C., the heat transfer fluidsmentioned herein have a specific heat (c_(p)) from about 1.25 kJ/kg·K toabout 3.50 kJ/kg·K, or from about 1.35 kJ/kg·K to about 3.40 kJ/kg·K, orfrom about 1.45 kJ/kg·K to about 3.25 kJ/kg·K, or from about 1.50kJ/kg·K to about 3.20 kJ/kg·K, or from about 1.55 kJ/kg·K to about 3.15kJ/kg·K.

In another embodiment, at a temperature of 80° C., the heat transferfluids mentioned herein have a specific heat (c_(p)) from about 1.25kJ/kg·K to about 3.50 kJ/kg·K, or from about 1.35 kJ/kg·K to about 3.40kJ/kg·K, or from about 1.45 kJ/kg·K to about 3.25 kJ/kg·K, or from about1.50 kJ/kg·K to about 3.20 kJ/kg·K, or from about 1.55 kJ/kg·K to about3.15 kJ/kg·K.

In an embodiment, where the average fluid temperature is 40° C., theheat transfer fluids mentioned herein have a dynamic viscosity (μ) fromabout 0.50 centipoise (cP) to about 7.50 cP, or from about 0.55 cP toabout 7.00 cP, or from about 0.65 cP to about 6.50 cP, or from about0.70 cP to about 6.00 cP, or from about 0.75 cP to about 5.50 cP.

In another embodiment, where the average fluid temperature is 80° C.,the heat transfer fluids mentioned herein have a dynamic viscosity (μ)from about 0.50 cP to about 7.50 cP, or from about 0.55 cP to about 7.00cP, or from about 0.65 cP to about 6.50 cP, or from about 0.70 cP toabout 6.00 cP, or from about 0.75 cP to about 5.50 cP.

In some aspects, when heat conveyance is the dominant mode controllingperformance of the heat transfer fluid in an application, thedimensional effectiveness factor (DEF_(fluid)) equation dependencies onfluid properties for the specified fluid circulation flow regimes andpump types are as follows:

1) for positive displacement pump and laminar heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) areρ¹ c_(p) ¹ μ⁻¹;

2) for positive displacement pump and transitional heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) areρ^(0.25) c_(p) ¹ μ^(−0.25);

3) for positive displacement pump and turbulent heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) arec_(p) ¹;

4) for centrifugal pump and laminar heat transfer circuit dominant flowregime, both the DEF_(fluid) and the DEF_(reference) are ρ^(0.19) c_(p)¹ μ^(−0.19);

5) for centrifugal pump and transitional heat transfer circuit dominantflow regime, both the DEF_(fluid) and the DEF reference are ρ^(0.04)c_(p) ¹ μ^(−0.04); and

6) for centrifugal pump and turbulent heat transfer circuit dominantflow regime, both the DEF_(fluid) and the DEF_(reference) are c_(p) ¹.

In one or more additional aspects, when heat conveyance is the dominantmode controlling performance of the heat transfer fluid in anapplication, the dimensional effectiveness factor (DEF_(fluid)) equationdependencies on fluid properties for the specified fluid circulationflow regimes and pump types are as follows:

1) for positive displacement pump and laminar heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) areρ^(0.5-1.5) c_(p) ^(0.5-1.5) μ^(−1.5-0.5);

2) for positive displacement pump and transitional heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) areρ^(0.5-1.5) c_(p) ^(0.5-1.5) μ^(−0.5-0.1);

3) for positive displacement pump and transitional heat transfer circuitdominant flow regime, both the DEF_(fluid) and the DEF_(reference) arec_(p) ^(0.5-1.5);

4) for centrifugal pump and laminar heat transfer circuit dominant flowregime, both the DEF_(fluid) and the DEF_(reference) are ρ^(0.5-1.5)c_(p) ^(0.5-1.5) μ^(−0.5-0.05);

5) for centrifugal pump and transitional heat transfer circuit dominantflow regime, both the DEF_(fluid) and the DEF_(reference) areρ^(0.01-0.1) c_(p) ^(0.5-1.5) μ^(−0.1-0.01); and

6) for centrifugal pump and turbulent heat transfer circuit dominantflow regime, both the DEF_(fluid) and the DEF_(reference) are c_(p)^(0.5-1.5).

The foregoing dimensional effectiveness factor (DEF_(fluid)) equationdependencies are provided merely for illustrative purposes when heatconveyance is the dominant mode controlling performance of the heattransfer fluid. In applications where localized heat transfer (i.e.,thermal conductivity) is instead the dominant mode controllingperformance of the heat transfer fluid in a cooling application, theequation dependencies would be different. Accordingly, the foregoingdimensional effectiveness factor (DEF_(fluid)) equation dependencies aremerely provided for illustrative purposes and should not be consideredparticularly limiting to the principles of the present disclosure.

The heat transfer fluids mentioned herein provide sustained heattransfer fluid properties over the lifetime of the heat transfer fluid,and compatibility with the electrical systems mentioned herein, e.g., anelectric vehicle and its components and materials. Illustrative electricvehicle components that can be cooled in accordance with this disclosureinclude, for example, electric vehicle batteries, electric motors,electric generators, AC-DC/DC-AC/AC-AC/DC-DC converters,AC-DC/DC-AC/AC-AC/DC-DC transformers, power management systems,electronics controlling batteries, on-board chargers, on-board powerelectronics, super-fast charging systems, fast charging equipment atcharging stations, stationary super-fast chargers, and the like.

Depending on the particular electric system (e.g., electric vehiclebatteries, electric motors, electric generators, AC-DC/DC-AC/AC-AC/DC-DCconverters, AC-DC/DC-AC/AC-AC/DC-DC transformers, power managementsystems, electronics controlling batteries, on-board chargers, on-boardpower electronics, super-fast charging systems, fast charging equipmentat charging stations, stationary super-fast chargers, and the like), theelectric system can operate over a wide temperature range. For example,the electric system can operate at a temperature between about −40° C.and about 175° C., or between about −25° C. and about 170° C., orbetween about −10° C. and about 165° C., or between about 0° C. andabout 160° C., or between about 10° C. and about 155° C., or betweenabout 25° C. and about 150° C., or between about 25° C. and about 125°C., or between about 30° C. and about 120° C., or between about 35° C.and about 115° C., or between about 35° C. and about 105° C., or betweenabout 35° C. and about 95° C., or between about 35° C. and about 85° C.

In an embodiment, a single heat transfer fluid can be used in theelectric system. In another embodiment, more than one heat transferfluid can be used in the electric system, for example, one heat transferfluid for the battery and another heat transfer fluid for anothercomponent of the electric system.

The heat transfer fluids mentioned herein provide advantaged performanceon surfaces of apparatus components that include, for example, thefollowing: metals, metal alloys, non-metals, non-metal alloys, mixedcarbon-metal composites and alloys, mixed carbon-nonmetal composites andalloys, ferrous metals, ferrous composites and alloys, non-ferrousmetals, non-ferrous composites and alloys, titanium, titanium compositesand alloys, aluminum, aluminum composites and alloys, magnesium,magnesium composites and alloys, ion-implanted metals and alloys, plasmamodified surfaces; surface modified materials; coatings; mono-layer,multi-layer, and gradient layered coatings; honed surfaces; polishedsurfaces; etched surfaces; textured surfaces; micro and nano structureson textured surfaces; super-finished surfaces; diamond-like carbon(DLC), DLC with high-hydrogen content, DLC with moderate hydrogencontent, DLC with low-hydrogen content, DLC with near-zero hydrogencontent, DLC composites, DLC-metal compositions and composites,DLC-nonmetal compositions and composites; ceramics, ceramic oxides,ceramic nitrides, FeN, CrN, ceramic carbides, mixed ceramiccompositions, and the like; polymers, thermoplastic polymers, engineeredpolymers, polymer blends, polymer alloys, polymer composites; materialscompositions and composites, that include, for example, graphite,carbon, molybdenum, molybdenum disulfide, polytetrafluoroethylene,polyperfluoropropylene, polyperfluoroalkylethers, and the like.

Referring to FIG. 1 , illustrated is a schematic diagram of an exampleheat transfer system 100 that may incorporate the principles of thepresent disclosure. The heat transfer system 100 includes a heattransfer circuit 102 that includes one or more conduits 104 and a pump106 configured to circulate a heat transfer fluid through the conduit(s)104. The pump 106 may comprise, for example, a positive displacementpump or a centrifugal pump. The heat transfer fluid may comprise any ofthe non-aqueous, dielectric heat transfer fluids mentioned herein, andmay be used to cool an electrical component 108 that forms part of anelectric system. The electrical component 108 exhibits a heat transferarea A_(hot) and the heat transfer fluid may be configured to directlycool one or more surfaces of the electrical component 108. Morespecifically, the heat transfer fluid may directly contact theelectrical component 108 and thereby draw heat away from the electricalcomponent 108.

A rate of heat conveyance (Q) is required to maintain the electricalcomponent 108 at a temperature of Te. Heat is removed from theelectrical component 108 by circulating the heat transfer fluid with aheat capacity (c_(p)) into direct contact with the electrical component108. The heat transfer fluid first contacts the electrical component 108with a low (cold) temperature of Tc. After exchanging heat with theelectrical component 108, the heat transfer fluid is conveyed away fromthe electrical component 108 at an elevated temperature of Th. Thewarmed heat transfer fluid is then conveyed within the conduit(s) 104 toa heat exchanger 110 included in the heat transfer circuit 102. The heatexchanger 110 may operate similar to a radiator by drawing heat awayfrom the heat transfer fluid. In some cases, the heat exchanger 110 mayreject heat to another heat transfer fluid, or, as illustrated, to airat ambient temperature Ta. The heat exchanger 110 (with heat transferarea A_(cold)) could be a specific device, or, simply heat lost to theatmosphere as the heat transfer fluid flows through the conduit(s) 104.

The pump 106 circulates the heat transfer fluid through the heattransfer circuit 102 at a mass flowrate of {dot over (m)}. At steadystate, the rate of heat conveyance (Q) is determined by the followingequation:

Q={dot over (m)}°c _(p)°(Th°−Tc)={dot over (V)}ρ°c _(p)°(Th°−Tc)

where {dot over (V)} is the volumetric flowrate and ρ is the fluiddensity. Depending on the type of pump 106 and the resulting flowrate ofthe heat transfer fluid, and further depending on the configuration andsurface areas Ahot and Acold of the electrical component 108 and theheat exchanger 108, the dominant flow regime of the heat transfercircuit may be laminar, transient, or turbulent.

Within the heat transfer circuit 102, cooling of the electricalcomponent 108 can be dominated by the ability of the fluid to “conveyheat” from the electrical component 108, or, can be dominated by the“localized heat transfer” mechanisms within electrical component 108.Many different equipment design and operation factors can dictate whichof these two phenomena are dominant. For example, in the electricalcomponent 108 (i.e., the element to be cooled), localized heat transfercould be enhanced by the inclusion of cooling fins in the equipmentdesign which increases the effective heat transfer area. Similarly,localized heat transfer could be improved by the artificial induction ofturbulence or boosted by enhancing fluid/hardware contact via fluid jetflow within the element. For any specific electric system, whether dueto basic design or through targeted design enhancements, it is possiblethat this localized heat transfer is not the dominant mechanismcontrolling heat transfer performance, but instead, the heat transferfluid's performance may be dominated by the ability of the heat transferfluid to convey heat away from the electrical component 108. The maximumamount of heat that could be conveyed by the heat transfer fluid isgiven by:

Q _(max) ={dot over (V)}ρc _(p)(Te−Ta)

The actual heat conveyed from the electrical component 108 is given by:

Q _(actual) ={dot over (V)}ρc _(p)(Th−Tc)

The heat transfer system 100 is considered to be dominated by localizedheat transfer if the actual heat being conveyed is less than or equal tohalf of maximum amount of heat that could be conveyed, i.e.,

$\frac{Q_{actual}}{Q_{\max}} \leq {0.5 - {``{{Localized}{heat}{transfer}{dominated}}"}}$

Conversely, if the actual amount of heat conveyed is more than half ofthe maximum possible amount of heat that could be conveyed by the fluid,the heat transfer system 100 is considered to be dominated by “heatconveyance”, i.e.,

$\frac{Q_{actual}}{Q_{\max}} > {0.5 - {``{{Heat}{conveyance}{dominated}}"}}$

Since the Mouromtseff equation (or number) attempts to relate the heattransfer fluid's localized heat transfer coefficient to fluidproperties, historic discussions regarding heat transfer fluids whichrefer to the Mouromtseff equation are only meaningful in “localized heattransfer dominated” applications, and bear little relevance in “heatconveyance dominated” applications. Further, it should be noted thatunlike the Mouromtseff equation, the DEF and NEF effectiveness factorsdescribed herein capture both the heat transfer performance and theenergy required to circulate the fluid.

According to embodiments of the present disclosure, the normalizedeffectiveness factor (NEF_(fluid)) of the heat transfer fluidcirculating through the heat transfer circuit 102 may be determined(calculated) to help understand and predict the real-time health of theheat transfer fluid. By understanding the impact of density, viscosity,heat capacity, and thermal conductivity, and the specific design of theelectric device on the efficacy of a heat transfer fluid, the real-timehealth or viability of the heat transfer fluid can be evaluated duringuse. To help accomplish this, the heat transfer system 100 may furtherinclude one or more sensors in communication with the heat transfercircuit 102 and configured to obtain real-time measurements of thedensity (ρ), the specific heat (c_(p)), the dynamic viscosity (μ), andthe thermal conductivity (k) of the heat transfer fluid circulatingwithin the heat transfer circuit 102. In the illustrated embodiment, theheat transfer system 100 includes a density sensor 112 a configured tomeasure the density (ρ) of the heat transfer fluid, a viscosity sensor112 b configured to measure the dynamic viscosity (μ) of the heattransfer fluid, a heat capacity sensor 112 c configured to measure thespecific heat (c_(p)) of the heat transfer fluid, and a thermalconductivity sensor 112 d configured to measure the thermal conductivity(k) of the heat transfer fluid.

The sensors 112 a-d may be in communication (either wired or wirelessly)with a computer system 114. Measurements obtained by the sensors 112 a-dmay be communicated to the computer system 114 for processing. Thecomputer system 114 may be programmed and otherwise configured to usethe measurements obtained by the sensors 112 a-d to help calculate thedimensional effectiveness factors (DEF_(fluid)) and (DEF_(reference))for a selected pump 106 and a selected dominant flow regime within theheat transfer circuit 102.

Moreover, the computer system 114 may then be programmed and otherwiseconfigured to determine or otherwise calculate the normalizedeffectiveness factor (NEF_(fluid)) of the heat transfer fluid, which canhelp determine the health of the heat transfer fluid. If the value ofthe NEF_(fluid) is at or above a predetermined threshold, for example,the health of the heat transfer fluid may be considered viable or stilleffective in helping remove heat from the electrical component 106. Incontrast, if the value of the NEF_(fluid) is below the predeterminedthreshold, the health of the heat transfer fluid may be considereddeteriorated or no longer effective. In some embodiments, thepredetermined threshold for the value of the NEF_(fluid) of the heattransfer fluid may be 1.0.

In some embodiments, once the value of the NEF_(fluid) for the heattransfer fluid falls below the predetermined threshold, the computersystem 114 may be configured to send an alert to the user (operator)indicating the same. In such embodiments, the user may then decide tohave the heat transfer fluid replaced or replenished, as desired. Inother embodiments, especially in embodiments with autonomous vehiclesand the like, once the value of the NEF_(fluid) for the heat transferfluid falls below the predetermined threshold, the computer system 114may be configured to direct the autonomous vehicle to a maintenancestation where the heat transfer fluid may be replaced or replenished.

Since the efficacy (viability) of the heat transfer fluid impacts theperformance of the heat transfer system 100, a comparison of thereal-time efficacy of the heat transfer fluid with the overall efficacyof the heat transfer system 100 may help diagnose whether diminishingcooling performance is from the degradation of the heat transfer fluid,or alternatively from an overall hardware issue. In other words,determining or otherwise calculating the normalized effectiveness factor(NEF_(fluid)) of the heat transfer fluid may also help diagnose whetherincreased operating temperature of an electrical device is related to adeteriorating heat transfer fluid or whether it stems from a hardwareissue related to the electrical device. More specifically, if the valueof the NEF_(fluid) remains at or above the predetermined threshold, butthe operating temperature of the electrical device continues toincrease, the health of the heat transfer fluid may be considered viableor still effective in helping remove heat from the electrical component106. Instead, the cause for the increased operating temperature islikely related to a hardware issue of the heat transfer system 100.Example hardware issues include, but are not limited to, fouling of theelectrical component 108, an improperly functioning pump 106, etc.

In embodiments where it is determined that the health of the heattransfer fluid remains viable, but a hardware issue of the heat transfersystem 100 may be at fault, the computer system 114 may be configured tosend an alert to the user (operator) indicating the same. In suchembodiments, the user may then decide to perform maintenance on thehardware of the electric device. In other embodiments, especially inembodiments with autonomous vehicles and the like, when it is determinedthat a hardware issue is causing increased temperatures in the heattransfer system 100, the computer system 114 may be configured to directthe autonomous vehicle to a maintenance station where the hardware maybe analyzed and the hardware issue may potentially be resolved.

In some embodiments, one or more of the sensors 112 a-d may form anintegral part of the heat transfer circuit 102. In such embodiments, forexample, the sensors 112 a-d may comprise internal or on-vehicle sensorsin an electric vehicle that are in constant fluid communication with theheat transfer circuit 102. Moreover, in such embodiments, measurementsmay be taken with the sensors 112 autonomously continuously,semi-continuously, at predetermined intervals, or as directed by thecomputer system 114 or an operator.

In other embodiments, however, one or more of the sensors 112 a-d may belocated external to the heat transfer circuit 102. In such embodiments,a sample of the heat transfer fluid may be obtained (extracted) from theheat transfer circuit 102 and transported to where the sensors 112 a-dare located for analysis. In at least one embodiment, obtaining thesample of the heat transfer fluid may be similar to obtaining a sampleof the oil in an internal combustion engine, or may alternatively beaccomplished via any other known means. Moreover, in such embodiments,samples of the heat transfer fluid may be obtained at predeterminedintervals or whenever an operator desires to check the health of theheat transfer fluid.

FIG. 2 illustrates an example embodiment of the computer system 114 ofFIG. 1 . As shown, the computer system 114 includes one or moreprocessors 202, which can control the operation of the computer system114. “Processors” are also referred to herein as “controllers.” Theprocessor(s) 202 can include any type of microprocessor or centralprocessing unit (CPU), including programmable general-purpose orspecial-purpose microprocessors and/or any one of a variety ofproprietary or commercially available single or multi-processor systems.The computer system 114 can also include one or more memories 204, whichcan provide temporary storage for code to be executed by theprocessor(s) 202 or for data acquired from one or more users, storagedevices, and/or databases. The memory 204 can include read-only memory(ROM), flash memory, one or more varieties of random access memory (RAM)(e.g., static RAM (SRAM), dynamic RAM (DRAM), or synchronous DRAM(SDRAM)), and/or a combination of memory technologies.

The various elements of the computer system 114 can be coupled to a bussystem 206. The illustrated bus system 206 is an abstraction thatrepresents any one or more separate physical busses, communicationlines/interfaces, and/or multi-drop or point-to-point connections,connected by appropriate bridges, adapters, and/or controllers. Thecomputer system 114 can also include one or more network interface(s)208, one or more input/output (IO) interface(s) 210, and one or morestorage device(s) 212.

The network interface(s) 208 can enable the computer system 114 tocommunicate with remote devices, e.g., other computer systems, over anetwork, and can be, for non-limiting example, remote desktop connectioninterfaces, Ethernet adapters, and/or other local area network (LAN)adapters. The IO interface(s) 210 can include one or more interfacecomponents to connect the computer system 114 with other electronicequipment. For non-limiting example, the 10 interface(s) 210 can includehigh-speed data ports, such as universal serial bus (USB) ports, 1394ports, Wi-Fi, Bluetooth, etc. Additionally, the computer system 114 canbe accessible to a human user, and thus the IO interface(s) 210 caninclude displays, speakers, keyboards, pointing devices, and/or variousother video, audio, or alphanumeric interfaces. The storage device(s)212 can include any conventional medium for storing data in anon-volatile and/or non-transient manner. The storage device(s) 212 canthus hold data and/or instructions in a persistent state, i.e., thevalue(s) are retained despite interruption of power to the computersystem 114. The storage device(s) 212 can include one or more hard diskdrives, flash drives, USB drives, optical drives, various media cards,diskettes, compact discs, and/or any combination thereof and can bedirectly connected to the computer system 114 or remotely connectedthereto, such as over a network. In an exemplary embodiment, the storagedevice(s) 212 can include a tangible or non-transitory computer readablemedium configured to store data, e.g., a hard disk drive, a flash drive,a USB drive, an optical drive, a media card, a diskette, a compact disc,etc.

The elements illustrated in FIG. 2 can be some or all of the elements ofa single physical machine. In addition, not all of the illustratedelements need to be located on or in the same physical machine.Exemplary computer systems include conventional desktop computers,workstations, minicomputers, laptop computers, tablet computers,personal digital assistants (PDAs), mobile phones, and the like.

The computer system 114 can include a web browser for retrieving webpages or other markup language streams, presenting those pages and/orstreams (visually, aurally, or otherwise), executing scripts, controlsand other code on those pages/streams, accepting user input with respectto those pages/streams (e.g., for purposes of completing input fields),issuing HyperText Transfer Protocol (HTTP) requests with respect tothose pages/streams or otherwise (e.g., for submitting to a serverinformation from the completed input fields), and so forth. The webpages or other markup language can be in HyperText Markup Language(HTML) or other conventional forms, including embedded Extensible MarkupLanguage (XML), scripts, controls, and so forth. The computer system 114can also include a web server for generating and/or delivering the webpages to client computer systems.

In an exemplary embodiment, the computer system 114 can be provided as asingle unit, e.g., as a single server, as a single tower, containedwithin a single housing, etc. The single unit can be modular such thatvarious aspects thereof can be swapped in and out as needed for, e.g.,upgrade, replacement, maintenance, etc., without interruptingfunctionality of any other aspects of the system. The single unit canthus also be scalable with the ability to be added to as additionalmodules and/or additional functionality of existing modules are desiredand/or improved upon.

The computer system 114 can also include any of a variety of othersoftware and/or hardware components, including by way of non-limitingexample, operating systems and database management systems. Although anexemplary computer system is depicted and described herein, it will beappreciated that this is for the sake of generality and convenience. Inother embodiments, the computer system may differ in architecture andoperation from that shown and described here.

The storage device(s) 212 may include one or more databases configuredto store and arrange data in the memory 204 and to interact with theprocessor 202. The data includes at least one fluid property selectedfrom the group consisting of density (ρ), specific heat (c_(p)), thermalconductivity (k), and dynamic viscosity (μ).

One of the components of the memory 204 may be a program module 214. Theprogram module 214 contains instructions for controlling the processor202 to execute the methods described herein. For example, as a result ofexecution of the program module 214, the processor 202 determines thedimensional effectiveness factor (DEF_(fluid)) of the heat transferfluid, the dimensional effectiveness factor (DEF_(reference)) of thereference fluid, and the normalized effectiveness factor (NEF_(fluid))of the heat transfer fluid. The processor 202 may then be programmed todetermine if the value of the NEF_(fluid) is at, above, or below apredetermined threshold, and thereby indicating the health of the heattransfer fluid as viable or deteriorated. The processor 202 outputs to auser interface of the network interface 208 a result of an execution ofthe methods described herein. Alternatively, the processor 202 coulddirect the output to a remote device (not shown) via the networkinterface 208.

The term “module” is used herein to denote a functional operation thatmay be embodied either as a stand-alone component or as an integratedconfiguration of a plurality of sub-ordinate components. Thus, theprogram module 214 may be implemented as a single module or as aplurality of modules that operate in cooperation with one another.Moreover, although the program module 214 is described herein as beinginstalled in the memory 204, and therefore being implemented insoftware, it could be implemented in any of hardware (e.g., electroniccircuitry), firmware, software, or a combination thereof.

While program module 214 is indicated as already loaded into memory 204,it may be configured on a storage medium 335 for subsequent loading intomemory 204. Storage medium 335 can be any conventional storage mediumthat stores program module 214 thereon in tangible form. Examples ofstorage medium 335 include a floppy disk, a compact disk, a magnetictape, a read only memory, an optical storage media, universal serial bus(USB) flash drive, a digital versatile disc, or a zip drive.Alternatively, storage medium 335 can be a random access memory, orother type of electronic storage, located on a remote storage system andcoupled to computer 305 via network 330.

Examples

The following non-limiting examples are provided to help illustratevarious aspects of the disclosure.

Case 1

In the electric vehicle design addressed in Case 1, there is a largesurface area across which heat is removed from hot surfaces of anelectric system. This is the case when, for instance, the battery to becooled has a large surface area available for cooling. As a result, theamount of heat flow from the hot surface to the heat transfer fluid isheat conveyance dominated. In the vehicle design addressed in this Case1, the cooling circuit design produces transitional flow (Reynoldsnumber between around 2100 and around 4000) dominates in the overallsystem, in order to achieve a balance between the pressure required tocirculate the heat transfer fluid and the size and weight of the coolingsystem. Finally, in the vehicle design addressed in this Case 1, aconstant flow (positive displacement) pump is employed, such that thevolume of heat transfer fluid being pumped through the system isindependent of the properties of the heat transfer fluid.

As a result, in this type of electric vehicle, the normalizedeffectiveness factor (NEF_(fluid)) will be proportional to the followingcombination of heat transfer fluid properties:

ρ^(0.25) *c _(p) ¹*μ^(−0.25).

Case 2

In the electric vehicle design addressed in Case 2, there is a largesurface area across which heat is removed from hot surfaces. This is thecase when, for instance, the battery to be cooled has a large surfacearea available for cooling. As a result, the amount of heat flow fromthe hot surface to the heat transfer fluid is heat conveyance dominated.In the vehicle design addressed in this Case 2, the cooling circuitdesign produces laminar flow (Reynolds number less than around 2100)throughout the system, in order to protect against damage to sensitivecomponents such as electronics and minimize the pressure required tocirculate the heat transfer fluid. Finally, in the vehicle designaddressed in this Case 2, a constant flow (positive displacement) pumpis employed, such that the volume of heat transfer fluid being pumpedthrough the system is independent of the properties of the heat transferfluid.

As a result, in this type of electric vehicle, the normalizedeffectiveness factor (NEF_(fluid)) will be proportional to the followingcombination of heat transfer fluid properties:

ρ¹ *c _(p) ¹*μ⁻¹.

Preparation of Heat Transfer Fluid Formulations and Testing Results

All of the ingredients used in the heat transfer fluid formulations arecommercially available. Heat transfer fluid formulations were preparedas described herein. Optional additives used in the formulations includeconventional additives in conventional amounts. Optional additives wereone or more of an antioxidant, corrosion inhibitor, antifoam agent, andantiwear additive.

Heat transfer fluids were prepared by blending at least one base stock,with one or more additives selected from an antioxidant, corrosioninhibitor, antifoam agent, and antiwear additive. Density (ρ) wasmeasured in accordance with ASTM D8085 or D4052. Specific heat (c_(p))was measured by ASTM E1269. Dynamic viscosity (μ) was measured by ASTMD8085 or derived from ASTM D445 and ASTM D4052. Dimensionaleffectiveness factor (DEF_(fluid)) equations for situations where heatconveyance is the dominant mechanism controlling performance of the heattransfer fluid in an application are given in Table 1 herein.

The normalized effectiveness factor (NEF_(fluid)) was determined by theequation:

${{{NE}F_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}};$

wherein DEF_(fluid) is a dimensional effectiveness factor for the heattransfer fluid that is determined based on an equation designated inTable 1 herein for a selected pump and a selected cooling circuitdominant flow regime; and wherein DEF_(reference) is a dimensionaleffectiveness factor for a reference fluid that is determined using thesame equation designated in Table 1 for DEF_(fluid) above for the sameselected pump and the same selected cooling circuit dominant flowregime. Both DEF_(fluid) and DEF_(reference) were determined at the samepredetermined temperature (i.e., 40° C. or 80° C.), and matching unitsfor each property were used in each equation.

Over the years, researchers have developed many pressure dropcorrelations. As an example, one of the most widely utilizedcorrelations for calculating the pressure drop due to laminar flow in apipe is the Hagen-Poiseuille equation is commonly used for. The specificcorrelation to use will be dependent on the geometry and flow regimewhere the majority of pressure drop through the circuit occurs. For thisdisclosure, use was made of correlations for the “Fanning frictionfactor”, f, which is defined as:

$f = {{\frac{1}{4} \circ d}\frac{\Delta P}{L}\frac{1}{\frac{1}{2}\rho\upsilon^{2}}}$

where f is the Fanning friction factor, d is the tube/pipe diameter, ΔPis the pressure drop, L is the equivalent length of tube/pipe, ρ is theaverage fluid density, and v is the fluid velocity.

Correlations for the friction factor have been developed as a functionof the Reynolds number as:

${Re} = \frac{d{\upsilon\rho}}{\mu}$

Laminar flow is defined as when the Re<2,100. In this flow regime, thefriction factor, f, is given by:

$f = \frac{16}{Re}$

Transitional flow is defined as when the Re>2,100 and its frictionfactor can be described by the Blasius equation, listed below:

$f = \frac{{0.0}791}{Re^{{0.2}5}}$

Transition to fully turbulent flow depends on the roughness of the pipe.For smooth pipes, the Blasius equation above can be valid up to aReynolds number of 10⁷. For specific applications, reference can be madeto charts in references like R. B. Bird, W. E. Stewart and E. N.Lightfoot, “Transport Phenomena”, John Wiley & Sons, New York, 1960,where based on the roughness of the specific application, deviation fromthe Blasius equation can be determined.

While these specific correlations have been used to derive the exponentson the properties in the factors for this disclosure, it should be notedthat any specific pressure drop correlation could be used for anyspecific application. Equally, this approach could be used for any otherapplication, like for example, flow over the outside of a tube bank, or,axial flow through concentric rotating cylinders, like for instancewhich may be encountered when directly cooling a rotor/stator.

Heat Transfer Fluid Base Stocks and Cobase Stocks

A wide range of heat transfer fluid base oils is known in the art. Heattransfer fluid base oils that are useful in the present disclosure arenatural oils, mineral oils and synthetic oils, and unconventional oils(or mixtures thereof) can be used unrefined, refined, or rerefined (thelatter is also known as reclaimed or reprocessed oil). Unrefined oilsare those obtained directly from a natural or synthetic source and usedwithout added purification. These include shale oil obtained directlyfrom retorting operations, petroleum oil obtained directly from primarydistillation, and ester oil obtained directly from an esterificationprocess. Refined oils are similar to the oils discussed for unrefinedoils except refined oils are subjected to one or more purification stepsto improve at least one heat transfer fluid base oil property. Oneskilled in the art is familiar with many purification processes. Theseprocesses include solvent extraction, secondary distillation, acidextraction, base extraction, filtration, and percolation. Rerefined oilsare obtained by processes analogous to refined oils but using an oilthat has been previously used as a feedstock.

Groups I, II, III, IV and V are broad base oil stock categoriesdeveloped and defined by the American Petroleum Institute (APIPublication 1509; www.API.org) to create guidelines for heat transferfluid base oils. Group I base stocks have a viscosity index of betweenabout 80 to 120 and contain greater than about 0.03% sulfur and/or lessthan about 90% saturates. Group II base stocks have a viscosity index ofbetween about 80 to 120, and contain less than or equal to about 0.03%sulfur and greater than or equal to about 90% saturates. Group IIIstocks have a viscosity index greater than about 120 and contain lessthan or equal to about 0.03% sulfur and greater than about 90%saturates. Group IV includes polyalphaolefins (PAO). Group V base stockincludes base stocks not included in Groups I-IV. The Table 2 belowsummarizes properties of each of these five groups.

TABLE 2 Base Oil Properties Saturates Sulfur Viscosity Index Group I <90and/or  >0.03 and ≥80 and <120 Group II ≥90 and ≤0.03 and ≥80 and <120Group III ≥90 and ≤0.03 and ≥120 Group IV polyalphaolefins (PAO) Group VAll other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lardoil, for example), and mineral oils. Animal and vegetable oilspossessing favorable thermal oxidative stability can be used. Of thenatural oils, mineral oils are preferred. Mineral oils vary widely as totheir crude source, for example, as to whether they are paraffinic,naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal orshale are also useful. Natural oils vary also as to the method used fortheir production and purification, for example, their distillation rangeand whether they are straight run or cracked, hydrorefined, or solventextracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks,including synthetic oils such as alkyl aromatics and synthetic estersare also well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oilssuch as polymerized and interpolymerized olefins (polybutylenes,polypropylenes, propylene isobutylene copolymers, ethylene-olefincopolymers, and ethylene-alphaolefin copolymers, for example).Polyalphaolefin (PAO) oil base stocks are commonly used synthetichydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄olefins or mixtures thereof may be utilized. See U.S. Pat. Nos.4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are knownmaterials and generally available on a major commercial scale fromsuppliers such as ExxonMobil Chemical Company, Chevron Phillips ChemicalCompany, BP, and others, typically vary from about 250 to about 3,000,although PAO's may be made in viscosities up to about 350 cSt (100° C.).The PAOs are typically comprised of relatively low molecular weighthydrogenated polymers or oligomers of alphaolefins which include, butare not limited to, C₂ to about C₃₂ alphaolefins with the C₈ to aboutC₁₆ alphaolefins, such as 1-octene, 1-decene, 1-dodecene and the like,being preferred. The preferred polyalphaolefins are poly-1-octene,poly-1-decene and poly-1-dodecene and mixtures thereof and mixedolefin-derived polyolefins. However, the dimers of higher olefins in therange of C₁₄ to C₁₈ may be used to provide low viscosity base stocks ofacceptably low volatility. Depending on the viscosity grade and thestarting oligomer, the PAOs may be predominantly trimers and tetramersof the starting olefins, with minor amounts of the higher oligomers,having a viscosity range of 1.5 to 12 cSt. PAO fluids of particular usemay include 3.0 cSt, 3.4 cSt, and/or 3.6 cSt and combinations thereof.Mixtures of PAO fluids having a viscosity range of 1.5 to approximately350 cSt or more may be used if desired.

The PAO fluids may be conveniently made by the polymerization of analphaolefin in the presence of a polymerization catalyst such as theFriedel-Crafts catalysts including, for example, aluminum trichloride,boron trifluoride or complexes of boron trifluoride with water, alcoholssuch as ethanol, propanol or butanol, carboxylic acids or esters such asethyl acetate or ethyl propionate. For example the methods disclosed byU.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein.Other descriptions of PAO synthesis are found in the following U.S. Pat.Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156;4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ toC₁₈ olefins are described in U.S. Pat. No. 4,218,330.

Other useful heat transfer fluid oil base stocks include wax isomeratebase stocks and base oils, comprising hydroisomerized waxy stocks (e.g.waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms,etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) basestocks and base oils, and other wax isomerate hydroisomerized basestocks and base oils, or mixtures thereof. Fischer-Tropsch waxes, thehigh boiling point residues of Fischer-Tropsch synthesis, are highlyparaffinic hydrocarbons with very low sulfur content. Thehydroprocessing used for the production of such base stocks may use anamorphous hydrocracking/hydroisomerization catalyst, such as one of thespecialized lube hydrocracking (LHDC) catalysts or a crystallinehydrocracking/hydroisomerization catalyst, preferably a zeoliticcatalyst. For example, one useful catalyst is ZSM-48 as described inU.S. Pat. No. 5,075,269, the disclosure of which is incorporated hereinby reference in its entirety. Processes for makinghydrocracked/hydroisomerized distillates andhydrocracked/hydroisomerized waxes are described, for example, in U.S.Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as inBritish Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Eachof the aforementioned patents is incorporated herein in their entirety.Particularly favorable processes are described in European PatentApplication Nos. 464546 and 464547, also incorporated herein byreference. Processes using Fischer-Tropsch wax feeds are described inU.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which areincorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils,and other wax-derived hydroisomerized (wax isomerate) base oils beadvantageously used in the instant disclosure, and may have usefulkinematic viscosities at 100° C. of about 3 cSt to about 50 cSt,preferably about 3 cSt to about 30 cSt, more preferably about 3.5 cSt toabout 25 cSt, as exemplified by GTL 4 with kinematic viscosity of about4.0 cSt at 100° C. and a viscosity index of about 141. TheseGas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils,and other wax-derived hydroisomerized base oils may have useful pourpoints of about −20° C. or lower, and under some conditions may haveadvantageous pour points of about −25° C. or lower, with useful pourpoints of about −30° C. to about −40° C. or lower. Useful compositionsof Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived baseoils, and wax-derived hydroisomerized base oils are recited in U.S. Pat.Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and areincorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as a base oil or base oilcomponent and can be any hydrocarbyl molecule that contains at leastabout 5% of its weight derived from an aromatic moiety such as abenzenoid moiety or naphthenoid moiety, or their derivatives. Thesehydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyldiphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylatedbis-phenol A, alkylated thiodiphenol, and the like. The aromatic can bemono-alkylated, dialkylated, polyalkylated, and the like. The aromaticcan be mono- or poly-functionalized. The hydrocarbyl groups can also becomprised of mixtures of alkyl groups, alkenyl groups, alkynyl,cycloalkyl groups, cycloalkenyl groups and other related hydrocarbylgroups. The hydrocarbyl groups can range from about C₆ up to about Chowith a range of about C₈ to about C₂₀ often being preferred. A mixtureof hydrocarbyl groups is often preferred, and up to about three suchsubstituents may be present. The hydrocarbyl group can optionallycontain sulfur, oxygen, and/or nitrogen containing substituents. Thearomatic group can also be derived from natural (petroleum) sources,provided at least about 5% of the molecule is comprised of an above-typearomatic moiety. Viscosities at 100° C. of approximately 3 cSt to about50 cSt are preferred, with viscosities of approximately 3.4 cSt to about20 cSt often being more preferred for the hydrocarbyl aromaticcomponent. In one embodiment, an alkyl naphthalene where the alkyl groupis primarily comprised of 1-hexadecene is used. Other alkylates ofaromatics can be advantageously used. Naphthalene or methyl naphthalene,for example, can be alkylated with olefins such as octene, decene,dodecene, tetradecene or higher, mixtures of similar olefins, and thelike. Useful concentrations of hydrocarbyl aromatic in a heat transferfluid composition can be about 2% to about 25%, preferably about 4% toabout 20%, and more preferably about 4% to about 15%, depending on theapplication.

Alkylated aromatics such as the hydrocarbyl aromatics of the presentdisclosure may be produced by well-known Friedel-Crafts alkylation ofaromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G.A. (ed.), Inter-science Publishers, New York, 1963. For example, anaromatic compound, such as benzene or naphthalene, is alkylated by anolefin, alkyl halide or alcohol in the presence of a Friedel-Craftscatalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1,chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-sciencePublishers, New York, 1964. Many homogeneous or heterogeneous, solidcatalysts are known to one skilled in the art. The choice of catalystdepends on the reactivity of the starting materials and product qualityrequirements. For example, strong acids such as AlCl₃, BF₃, or HF may beused. In some cases, milder catalysts such as FeCl₃ or SnCl₄ arepreferred. Newer alkylation technology uses zeolites or solid superacids.

Esters comprise a useful base stock. Additive solvency and sealcompatibility characteristics may be secured by the use of esters suchas the esters of dibasic acids with monoalkanols and the polyol estersof monocarboxylic acids. Esters of the former type include, for example,the esters of dicarboxylic acids such as phthalic acid, succinic acid,alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid,suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc.,with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types ofesters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained byreacting one or more polyhydric alcohols, preferably the hinderedpolyols (such as the neopentyl polyols, e.g., neopentyl glycol,trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylolpropane, pentaerythritol and dipentaerythritol) with alkanoic acidscontaining at least about 4 carbon atoms, preferably C₅ to C₃₀ acidssuch as saturated straight chain fatty acids including caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, stearic acid,arachic acid, and behenic acid, or the corresponding branched chainfatty acids or unsaturated fatty acids such as oleic acid, or mixturesof any of these materials.

Suitable synthetic ester components include the esters of trimethylolpropane, trimethylol butane, trimethylol ethane, pentaerythritol and/ordipentaerythritol with one or more monocarboxylic acids containing fromabout 5 to about 10 carbon atoms. These esters are widely availablecommercially, for example, the Mobil P-41 and P-51 esters of ExxonMobilChemical Company.

Also useful are esters derived from renewable material such as coconut,palm, rapeseed, soy, sunflower and the like. These esters may bemonoesters, di-esters, polyol esters, complex esters, or mixturesthereof. These esters are widely available commercially, for example,the Mobil P-51 ester of ExxonMobil Chemical Company.

Heat transfer fluid formulations containing renewable esters areincluded in this disclosure. For such formulations, the renewablecontent of the ester is typically greater than about 70 weight percent,preferably more than about 80 weight percent and most preferably morethan about 90 weight percent.

Other useful fluids include non-conventional or unconventional basestocks that have been processed, preferably catalytically, orsynthesized to provide high performance heat transfer characteristics.

Non-conventional or unconventional base stocks/base oils include one ormore of a mixture of base stock(s) derived from one or moreGas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate basestock(s) derived from natural wax or waxy feeds, mineral and ornon-mineral oil waxy feed stocks such as slack waxes, natural waxes, andwaxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxyraffinate, hydrocrackate, thermal crackates, or other mineral, mineraloil, or even non-petroleum oil derived waxy materials such as waxymaterials received from coal liquefaction or shale oil, and mixtures ofsuch base stocks.

GTL materials are materials that are derived via one or more synthesis,combination, transformation, rearrangement, and/ordegradation/deconstructive processes from gaseous carbon-containingcompounds, hydrogen-containing compounds and/or elements as feedstockssuch as hydrogen, carbon dioxide, carbon monoxide, water, methane,ethane, ethylene, acetylene, propane, propylene, propyne, butane,butylenes, and butynes. GTL base stocks and/or base oils are GTLmaterials that are generally derived from hydrocarbons; for example,waxy synthesized hydrocarbons, that are themselves derived from simplergaseous carbon-containing compounds, hydrogen-containing compoundsand/or elements as feedstocks. GTL base stock(s) and/or base oil(s)include oils boiling in the lube oil boiling range (1)separated/fractionated from synthesized GTL materials such as, forexample, by distillation and subsequently subjected to a final waxprocessing step which involves either or both of a catalytic dewaxingprocess, or a solvent dewaxing process, to produce lube oils ofreduced/low pour point; (2) synthesized wax isomerates, comprising, forexample, hydrodewaxed or hydroisomerized cat and/or solvent dewaxedsynthesized wax or waxy hydrocarbons; (3) hydrodewaxed orhydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T)material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possibleanalogous oxygenates); preferably hydrodewaxed orhydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxyhydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (orsolvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials,especially, hydrodewaxed or hydroisomerized/followed by cat and/orsolvent dewaxed wax or waxy feed, preferably F-T material derived basestock(s) and/or base oil(s), are characterized typically as havingkinematic viscosities at 100° C. of from about 2 mm²/s to about 50 mm²/s(ASTM D445). They are further characterized typically as having pourpoints of −5° C. to about −40° C. or lower (ASTM D97). They are alsocharacterized typically as having viscosity indices of about 80 to about140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typicallyhighly paraffinic (>90% saturates), and may contain mixtures ofmonocycloparaffins and multicycloparaffins in combination withnon-cyclic isoparaffins. The ratio of the naphthenic (i.e.,cycloparaffin) content in such combinations varies with the catalyst andtemperature used. Further, GTL base stock(s) and/or base oil(s)typically have very low sulfur and nitrogen content, generallycontaining less than about 10 ppm, and more typically less than about 5ppm of each of these elements. The sulfur and nitrogen content of GTLbase stock(s) and/or base oil(s) obtained from F-T material, especiallyF-T wax, is essentially nil. In addition, the absence of phosphorous andaromatics make this materially especially suitable for the formulationof low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stockand/or base oil is to be understood as embracing individual fractions ofsuch materials of wide viscosity range as recovered in the productionprocess, mixtures of two or more of such fractions, as well as mixturesof one or two or more low viscosity fractions with one, two or morehigher viscosity fractions to produce a blend wherein the blend exhibitsa target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s)is/are derived is preferably an F-T material (i.e., hydrocarbons, waxyhydrocarbons, wax).

Base oils for use in the formulated heat transfer fluids useful in thepresent disclosure are any of the variety of oils corresponding to APIGroup I, Group II, Group III, Group IV, and Group V oils, and mixturesthereof, preferably API Group II, Group III, Group IV, and Group V oils,and mixtures thereof, more preferably Group III, Group IV, and Group Vbase oils, and mixtures thereof. Highly paraffinic base oils can be usedto advantage in the formulated heat transfer fluids useful in thepresent disclosure. Minor quantities of Group I stock, such as theamount used to dilute additives for blending into formulated lube oilproducts, can also be used. Even in regard to the Group II stocks, it ispreferred that the Group II stock be in the higher quality rangeassociated with that stock, i.e. a Group II stock having a viscosityindex in the range 100<VI<120.

Preferred base fluids for use in the formulated heat transfer fluidsuseful in the present disclosure include, for example, aromatichydrocarbons, polyolefins, paraffins, isoparaffins, esters, ethers,fluorinated fluids, nano fluids, and silicone oils.

The base oil constitutes the major component of the heat transfer fluidcomposition of the present disclosure and typically is present in anamount ranging from about 50 to about 99 weight percent, preferably fromabout 70 to about 95 weight percent, and more preferably from about 85to about 95 weight percent, based on the total weight of thecomposition. The base oil conveniently has a kinematic viscosity,according to ASTM standards, of about 2.5 cSt to about 12 cSt (or mm²/s)at 100° C. and preferably of about 2.5 cSt to about 9 cSt (or mm²/s) at100° C. Mixtures of synthetic and natural base oils may be used ifdesired. Bi-modal mixtures of Group I, II, III, IV, and/or V base stocksmay be used if desired.

Heat Transfer Fluid Additives

The formulated heat transfer fluid useful in the present disclosure mayadditionally contain one or more commonly used heat transfer fluidperformance additives including but not limited to antioxidants,corrosion inhibitors, antifoam agents, nanomaterials, nanoparticles, andothers. These additives are commonly delivered with varying amounts ofdiluent oil, that may range from 5 weight percent to 50 weight percent.

The additives useful in this disclosure do not have to be soluble in theheat transfer fluids.

The types and quantities of performance additives used in combinationwith the instant disclosure in heat transfer fluid compositions are notlimited by the examples shown herein as illustrations.

Antioxidants

The heat transfer fluids typically include at least one antioxidant.Antioxidants retard the oxidative degradation of base oils duringservice. Such degradation may result in deposits on metal surfaces, thepresence of sludge, or a viscosity increase in the heat transfer fluid.One skilled in the art knows a wide variety of oxidation inhibitors thatare useful in heat transfer fluids. See, Klamann in Lubricants andRelated Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197,for example.

Illustrative antioxidants include sterically hindered alkyl phenols suchas 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol and2,6-di-tert-butyl-4-(2-octyl-3-propanoic) phenol; N,N-di(alkylphenyl)amines; and alkylated phenylenediamines.

The antioxidant may be a hindered phenolic antioxidant such as butylatedhydroxytoluene, suitably present in an amount of 0.01 to 5%, preferably0.4 to 0.8%, by weight of the heat transfer fluid. Alternatively, or inaddition, the antioxidant may comprise an aromatic amine antioxidantsuch as mono-octylphenylalphanapthyl amine or p,p-dioctyldiphenylamine,used singly or in admixture. The amine antioxidant component is suitablypresent in a range of from 0.01 to 5% by weight of the heat transferfluid, more preferably 0.5 to 1.5%.

Useful antioxidants include hindered phenols. These phenolicantioxidants may be ashless (metal-free) phenolic compounds or neutralor basic metal salts of certain phenolic compounds. Typical phenolicantioxidant compounds are the hindered phenolics, which are the onesthat contain a sterically hindered hydroxyl group, and these includethose derivatives of dihydroxy aryl compounds in which the hydroxylgroups are in the o- or p-position to each other. Typical phenolicantioxidants include the hindered phenols substituted with C₆+ alkylgroups and the alkylene coupled derivatives of these hindered phenols.Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol;2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol;2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol;2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecylphenol. Other useful hindered mono-phenolic antioxidants may include forexample hindered 2,6-di-alkyl-phenolic proprionic ester derivatives.Bis-phenolic antioxidants may also be advantageously used in combinationwith the instant disclosure. Examples of ortho-coupled phenols include:2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol);and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenolsinclude for example 4,4′-bis(2,6-di-t-butylphenol) and4,4′-methylene-bis(2,6-di-t-butylphenol).

Other illustrative phenolic antioxidants include sulfurized andnon-sulfurized phenolic antioxidants. The terms “phenolic type” or“phenolic antioxidant” used herein includes compounds having one or morethan one hydroxyl group bound to an aromatic ring which may itself bemononuclear, e.g., benzyl, or poly-nuclear, e.g., naphthyl and Spiroaromatic compounds. Thus “phenol type” includes phenol per se, catechol,resorcinol, hydroquinone, naphthol, etc., as well as alkyl or alkenyland sulfurized alkyl or alkenyl derivatives thereof, and bisphenol typecompounds including such bi-phenol compounds linked by alkylene bridgessulfuric bridges or oxygen bridges. Alkyl phenols include mono- andpoly-alkyl or alkenyl phenols, the alkyl or alkenyl group containingfrom 3-100 carbons, preferably 4 to 50 carbons and sulfurizedderivatives thereof, the number of alkyl or alkenyl groups present inthe aromatic ring ranging from 1 to up to the available unsatisfiedvalences of the aromatic ring remaining after counting the number ofhydroxyl groups bound to the aromatic ring.

Generally, therefore, the phenolic antioxidant may be represented by thegeneral formula:

(R)_(x) —Ar—(OH)_(y)

where Ar is selected from the group consisting of:

wherein R is a C₃-C₁₀₀ alkyl or alkenyl group, a sulfur substitutedalkyl or alkenyl group, preferably a C₄-C₅₀ alkyl or alkenyl group orsulfur substituted alkyl or alkenyl group, more preferably C₃-C₁₀₀ alkylor sulfur substituted alkyl group, most preferably a C₄-C₅₀ alkyl group,R^(g) is a C₁-C₁₀₀ alkylene or sulfur substituted alkylene group,preferably a C₂-C₅₀ alkylene or sulfur substituted alkylene group, morepreferably a C₂-C₂₀ alkylene or sulfur substituted alkylene group, y isat least 1 to up to the available valences of Ar, x ranges from 0 to upto the available valances of Ar-y, z ranges from 1 to 10, n ranges from0 to 20, and m is 0 to 4 and p is 0 or 1, preferably y ranges from 1 to3, x ranges from 0 to 3, z ranges from 1 to 4 and n ranges from 0 to 5,and p is 0.

Preferred phenolic antioxidant compounds are the hindered phenolics andphenolic esters which contain a sterically hindered hydroxyl group, andthese include those derivatives of dihydroxy aryl compounds in which thehydroxyl groups are in the o- or p-position to each other. Typicalphenolic antioxidants include the hindered phenols substituted withC.sub.1+ alkyl groups and the alkylene coupled derivatives of thesehindered phenols. Examples of phenolic materials of this type2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecylphenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol;2-methyl-6-t-butyl-4-heptyl phenol; 2-methyl-6-t-butyl-4-dodecyl phenol;2,6-di-t-butyl-4 methyl phenol; 2,6-di-t-butyl-4-ethyl phenol; and2,6-di-t-butyl 4 alkoxy phenol; and

Phenolic type antioxidants are well known in the heat transfer fluidindustry and commercial examples such as Ethanox™ 1710, Irganox™ 1076,Irganox™ L1035, Irganox™ 1010, Irganox™ L109, Irganox™ L118, Irganox™L135 and the like are familiar to those skilled in the art. The above ispresented only by way of exemplification, not limitation on the type ofphenolic antioxidants which can be used.

Other examples of phenol-based antioxidants include 2-t-butylphenol,2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol,2,4-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol,2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol,2,5-di-t-butylhydroquinone (manufactured by the Kawaguchi Kagaku Co.under trade designation “Antage DBH”), 2,6-di-t-butylphenol and2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butyl-4-methylphenol and2,6-di-t-butyl-4-ethylphenol; 2,6-di-t-butyl-4-alkoxyphenols such as2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol,3,5-di-t-butyl-4-hydroxybenzylmercaptoocty-1 acetate,alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such asn-octyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured bythe Yoshitomi Seiyaku Co. under the trade designation “Yonox SS”),n-dodecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and2′-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate;2,6-di-t-butyl-alpha-dimethyl amino-p-cresol,2,2′-methylenebis(4-alkyl-6-t-butylphenol) compounds such as2,2′-methylenebis(4-methyl-6-t-butylphe-nol) (manufactured by theKawaguchi Kagaku Co. under the trade designation “Antage W-400”) and2,2′-methylenebis(4-ethyl-6-t-butylphenol) (manufactured by theKawaguchi Kagaku Co. under the trade designation “Antage W-500”);bisphenols such as 4,4′-butylidenebis(3-methyl-6-t-butyl-phenol)(manufactured by the Kawaguchi Kagaku Co. under the trade designation“Antage W-300”), 4,4′-methylenebis(2,6-di-t-butylphenol) (manufacturedby Laporte Performance Chemicals under the trade designation “Ionox220AH”), 4,4′-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane(Bisphenol A), 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane,4,4′-cyclohexylidenebis(2,6-di-t-butylphenol), hexamethylene glycolbis[3, (3,5-di-t-butyl hydroxyphenyl)propionate] (manufactured by theCiba Specialty Chemicals Co. under the trade designation “IrganoxL109”), triethylene glycolbis[3-(3-t-butyl-4-hydroxy-y-5-methylphenyl)propionate] (manufactured bythe Yoshitomi Seiyaku Co. under the trade designation “Tominox 917”),2,2′-thio[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate](manufactured by the Ciba Specialty Chemicals Co. under the tradedesignation “Irganox L115”),3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane (manufactured by the SumitomoKagaku Co. under the trade designation “Sumilizer GA80”) and4,4′-thiobis(3-methyl-6-t-butylphenol) (manufactured by the KawaguchiKagaku Co. under the trade designation “Antage RC”),2,2′-thiobis(4,6-di-t-butylresorcinol); polyphenols such astetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionato[methane(manufactured by the Ciba Specialty Chemicals Co. under the tradedesignation “Irganox L101”),1,1,3-tris(2-methyl-4-hydroxy-5-t-butylpheny-l)butane (manufactured bythe Yoshitomi Seiyaku Co. under the trade designation “Yoshinox 930”),1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene(manufactured by Ciba Specialty Chemicals under the trade designation“Irganox 330”), bis[3,3′-bis(4′-hydroxy-3′-t-butylpheny-1)butyric acid]glycol ester,2-(3′,5′-di-t-butyl-4-hydroxyphenyl)-methyl-4-(2″,4″-di-t-butyl-3″-hyd-roxyphenyl)methyl-6-t-butylphenoland 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methylphenol; andphenol/aldehyde condensates such as the condensates of p-t-butylphenoland formaldehyde and the condensates of p-t-butylphenol andacetaldehyde.

Effective amounts of one or more catalytic antioxidants may also beused. The catalytic antioxidants comprise an effective amount of a) oneor more oil soluble polymetal organic compounds; and, effective amountsof b) one or more substituted N,N′-diaryl-o-phenylenediamine compoundsor c) one or more hindered phenol compounds; or a combination of both b)and c). Catalytic antioxidants are more fully described in U.S. Pat. No.8,048,833, herein incorporated by reference in its entirety.

Illustrative aromatic amine antioxidants include phenyl-alpha-naphthylamine which is described by the following molecular structure:

wherein R^(z) is hydrogen or a C₁ to C₁₄ linear or C₃ to C₁₄ branchedalkyl group, preferably C₁ to C₁₀ linear or C₃ to C₁₀ branched alkylgroup, more preferably linear or branched C₆ to C₈ and n is an integerranging from 1 to 5 preferably 1. A particular example is Irganox L06.

Other aromatic amine antioxidants include other alkylated andnon-alkylated aromatic amines such as aromatic monoamines.

Typical aromatic amines antioxidants have alkyl substituent groups of atleast 6 carbon atoms. Examples of aliphatic groups include hexyl,heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups willnot contain more than 14 carbon atoms. The general types of such otheradditional amine antioxidants which may be present includediphenylamines, phenothiazines, imidodibenzyls and diphenyl phenylenediamines. Mixtures of two or more of such other additional aromaticamines may also be present. Polymeric amine antioxidants can also beused.

The antioxidants or oxidation inhibitors that are useful in heattransfer fluids of the disclosure are the hindered phenols (e.g.,2,6-di-(t-butyl)phenol); aromatic amines (e.g., alkylated diphenylamines); alkyl polysulfides; selenides; borates (e.g., epoxide/boricacid reaction products); phosphorodithioic acids, esters and/or salts;and the dithiocarbamate (e.g., zinc dithiocarbamates). In an embodiment,these antioxidants or oxidation inhibitors can be employed individuallyor at ratios of amine/phenolic from 1:10 to 10:1 of the mixturespreferred.

The antioxidants or oxidation inhibitors that are also useful in heattransfer fluid compositions of the disclosure are chlorinated aliphatichydrocarbons such as chlorinated wax; organic sulfides and polysulfidessuch as benzyl disulfide, bis(chlorobenzyl)disulfide, dibutyltetrasulfide, sulfurized methyl ester of oleic acid, sulfurizedalkylphenol, sulfurized dipentene, and sulfurized terpene;phosphosulfiirized hydrocarbons such as the reaction product of aphosphorus sulfide with turpentine or methyl oleate, phosphorus estersincluding principally dihydrocarbon and trihydrocarbon phosphites suchas dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite,pentylphenyl phosphite, dipentylphenyl phosphite, tridecyl phosphite,distearyl phosphite, dimethyl naphthyl phosphite, oleyl 4-pentylphenylphosphite, polypropylene (molecular weight 500)-substituted phenylphosphite, diisobutyl-substituted phenyl phosphite; metalthiocarbamates, such as zinc dioctyldithiocarbamate, and bariumheptylphenyl dithiocarbamate; Group II metal phosphorodithioates such aszinc dicyclohexylphosphorodithioate, zinc dioctylphosphorodithioate,barium di(heptylphenyl)(phosphorodithioate, cadmiumdinonylphosphorodithioate, and the reaction of phosphorus pentasulfidewith an equimolar mixture of isopropyl alcohol, 4-methyl-2-pentanol, andn-hexyl alcohol.

Oxidation inhibitors including organic compounds containing sulfur,nitrogen, phosphorus and some alkylphenols are useful additives in theheat transfer fluid formulations of this disclosure. Two general typesof oxidation inhibitors are those that react with the initiators, peroxyradicals, and hydroperoxides to form inactive compounds, and those thatdecompose these materials to form less active compounds. Examples arehindered (alkylated) phenols, e.g.6-di(tert-butyl)-4-methyl-phenol[2,6-di(tert-butyl)-p-cresol, DBPC], andaromatic amines, e.g. N-phenyl-alpha-naphthalamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal saltsthereof also are useful antioxidants.

Another class of antioxidant used in heat transfer fluid compositionsand which may also be present are oil-soluble copper compounds. Anyoil-soluble suitable copper compound may be blended into the heattransfer fluid. Examples of suitable copper antioxidants include copperdihydrocarbyl thio- or dithio-phosphates and copper salts of carboxylicacid (naturally occurring or synthetic). Other suitable copper saltsinclude copper dithiacarbamates, sulphonates, phenates, andacetylacetonates. Basic, neutral, or acidic copper Cu(I) and or Cu(II)salts derived from alkenyl succinic acids or anhydrides are known to beparticularly useful.

A sulfur-containing antioxidant may be any and every antioxidantcontaining sulfur, for example, including dialkyl thiodipropionates suchas dilauryl thiodipropionate and distearyl thiodipropionate,dialkyldithiocarbamic acid derivatives (excluding metal salts),bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide, mercaptobenzothiazole,reaction products of phosphorus pentoxide and olefins, and dicetylsulfide. Of these, preferred are dialkyl thiodipropionates such asdilauryl thiodipropionate and distearyl thiodipropionate. The amine-typeantioxidant includes, for example, monoalkyldiphenylamines such asmonooctyldiphenylamine and monononyldiphenyl amine;dialkyldiphenylamines such as 4,4′-dibutyldiphenylamine,4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine,4,4′-diheptyldiphenylamine, 4,4′-dioctyldiphenylamine and4,4′-dinonyldiphenylamine; polyalkyldiphenylamines such astetrabutyldiphenylamine, tetrahexyldiphenylamine,tetraoctyldiphenylamine and tetranonyldiphenylamine; and naphthylaminessuch as alpha-naphthylamine, phenyl-alpha-naphthylamine,butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthyl amine,hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine,octylphenyl-alpha-naphthyl amine and nonylphenyl-alpha-naphthylamine. Ofthese, preferred are dialkyldiphenylamines.

Examples of sulphur-based antioxidants include dialkylsulphides such asdidodecylsulphide and dioctadecylsulphide; thiodipropionic acid esterssuch as didodecyl thiodipropionate, dioctadecyl thiodipropionate,dimyristyl thiodipropionate and dodecyloctadecyl thiodipropionate, and2-mercaptobenzimidazole.

Such antioxidants may be used individually or as mixtures of one or moretypes of antioxidants, the total amount employed being an amount ofabout 0.01 to about 5 wt %, preferably 0.1 to about 4.5 wt %, morepreferably 0.25 to 3 wt % (on an as-received basis).

Corrosion Inhibitors

The heat transfer fluid compositions can include at least one corrosioninhibitor. Corrosion inhibitors are used to reduce the degradation ofmetallic parts that are in contact with the heat transfer fluid oilcomposition. Suitable corrosion inhibitors include aryl thiazines, alkylsubstituted dimercaptothiodiazoles, alkyl substituteddimercaptothiadiazoles, and mixtures thereof.

Corrosion inhibitors are additives that protect metal surfaces againstchemical attack by water or other contaminants. A wide variety of theseare commercially available. As used herein, corrosion inhibitors includeantirust additives and metal deactivators.

One type of corrosion inhibitor is a polar compound that wets the metalsurface preferentially, protecting it with a film of oil. Another typeof corrosion inhibitor absorbs water by incorporating it in awater-in-oil emulsion so that only the oil touches the metal surface.Yet another type of corrosion inhibitor chemically adheres to the metalto produce a non-reactive surface. Examples of suitable additivesinclude zinc dithiophosphates, metal phenolates, basic metal sulfonates,fatty acids and amines. Such additives may be used in an amount of about0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Illustrative corrosion inhibitors include (short-chain) alkenyl succinicacids, partial esters thereof and nitrogen-containing derivativesthereof and synthetic alkarylsulfonates, such as metaldinonylnaphthalene sulfonates. Corrosion inhibitors include, forexample, monocarboxylic acids which have from 8 to 30 carbon atoms,alkyl or alkenyl succinates or partial esters thereof, hydroxy-fattyacids which have from 12 to 30 carbon atoms and derivatives thereof,sarcosines which have from 8 to 24 carbon atoms and derivatives thereof,amino acids and derivatives thereof, naphthenic acid and derivativesthereof, lanolin fatty acid, mercapto-fatty acids and paraffin oxides.

Particularly preferred corrosion inhibitors are indicated below.Examples of monocarboxylic acids (C₈-C₃₀), Caprylic acid, pelargonicacid, decanoic acid, undecanoic acid, lauric acid, myristic acid,palmitic acid, stearic acid, arachic acid, behenic acid, cerotic acid,montanic acid, melissic acid, oleic acid, docosanic acid, erucic acid,eicosenic acid, beef tallow fatty acid, soy bean fatty acid, coconut oilfatty acid, linolic acid, linoleic acid, tall oil fatty acid,12-hydroxystearic acid, laurylsarcosinic acid, myritsylsarcosinic acid,palmitylsarcosinic acid, stearylsarcosinic acid, oleylsarcosinic acid,alkylated (C₈-C₂₀) phenoxyacetic acids, lanolin fatty acid and C₈-C₂₄mercapto-fatty acids.

Examples of polybasic carboxylic acids which function as corrosioninhibitors include alkenyl (C₁₀-C₁₀₀) succinic acids and esterderivatives thereof, dimer acid, N-acyl-N-alkyloxyalkyl aspartic acidesters (U.S. Pat. No. 5,275,749). Examples of the alkylamines whichfunction as corrosion inhibitors or as reaction products with the abovecarboxylates to give amides and the like are represented by primaryamines such as laurylamine, coconut-amine, n-tridecylamine,myristylamine, n-pentadecylamine, palmitylamine, n-heptadecylamine,stearylamine, n-nonadecylamine, n-eicosylamine, n-heneicosylamine,n-docosylamine, n-tricosylamine, n-pentacosylamine, oleylamine, beeftallow-amine, hydrogenated beef tallow-amine and soy bean-amine.Examples of the secondary amines include dilaurylamine,di-coconut-amine, di-n-tri decyl amine, dimyristylamine,di-n-pentadecylamine, dipalmitylamine, di-n-pentadecylamine,distearylamine, di-n-nonadecylamine, di-n-eicosylamine,di-n-heneicosylamine, di-n-docosylamine, di-n-tricosylamine,di-n-pentacosyl-amine, dioleylamine, di-beef tallow-amine,di-hydrogenated beef tallow-amine and di-soy bean-amine. Examples of theaforementioned N-alkylpolyalkyenediamines include: ethylenediamines suchas laurylethylenediamine, coconut ethylenediamine,n-tridecylethylenediamine-, myristylethylenediamine,n-pentadecylethylenediamine, palmitylethylenediamine,n-heptadecylethylenediamine, stearylethylenediamine,n-nonadecylethylenediamine, n-eicosylethylenediamine,n-heneicosylethylenediamine, n-docosylethylendiamine,n-tricosylethylenediamine, n-pentacosylethylenediamine,oleylethylenediamine, beef tallow-ethylenediamine, hydrogenated beeftallow-ethylenediamine and soy bean-ethylenediamine; propylenediaminessuch as laurylpropylenediamine, coconut propylenediamine,n-tridecylpropylenediamine, myristylpropylenediamine,n-pentadecylpropylenediamine, palmitylpropylenediamine,n-heptadecylpropylenediamine, stearylpropylenediamine,n-nonadecylpropylenediamine, n-eicosylpropylenediamine,n-heneicosylpropylenediamine, n-docosylpropylendiamine,n-tricosylpropylenediamine, n-pentacosylpropylenediamine, diethylenetriamine (DETA) or triethylene tetramine (TETA), oleylpropylenediamine,beef tallow-propylenediamine, hydrogenated beef tallow-propylenediamineand soy bean-propylenediamine; butylenediamines such aslaurylbutylenediamine, coconut butylenediamine,n-tridecylbutylenediamine-myristylbutylenediamine,n-pentadecylbutylenediamine, stearylbutylenediamine,n-eicosylbutylenediamine, n-heneicosylbutylenedia-mine,n-docosylbutylendiamine, n-tricosylbutylenediamine,n-pentacosylbutylenediamine, oleylbutylenediamine, beeftallow-butylenediamine, hydrogenated beef tallow-butylenediamine and soybean butylenediamine; and pentylenediamines such aslaurylpentylenediamine, coconut pentylenediamine,myristylpentylenediamine, palmitylpentylenediamine,stearylpentylenediamine, oleyl-pentylenediamine, beeftallow-pentylenediamine, hydrogenated beef tallow-pentylenediamine andsoy bean pentylenediamine.

Other illustrative corrosion inhibitors include2,5-dimercapto-1,3,4-thiadiazoles and derivatives thereof,mercaptobenzothiazoles, alkyltriazoles and benzotriazoles. Examples ofdibasic acids useful as corrosion inhibitors, which may be used in thepresent disclosure, are sebacic acid, adipic acid, azelaic acid,dodecanedioic acid, 3-methyladipic acid, 3-nitrophthalic acid,1,10-decanedicarboxylic acid, and fumaric acid. The corrosion inhibitorscan be a straight or branch-chained, saturated or unsaturatedmonocarboxylic acid or ester thereof, which may optionally besulphurised in an amount up to 35% by weight. Preferably the acid is aC₄ to C₂₂ straight chain unsaturated monocarboxylic acid. The preferredconcentration of this additive is from 0.001% to 0.35% by weight of thetotal heat transfer fluid composition. The preferred monocarboxylic acidis sulphurised oleic acid. However, other suitable materials are oleicacid itself; valeric acid and erucic acid. An illustrative corrosioninhibitor includes a triazole as previously defined. The triazole shouldbe used at a concentration from 0.005% to 0.25% by weight of the totalcomposition. The preferred triazole is tolylotriazole which may beincluded in the compositions of the disclosure include triazoles,thiazoles and certain diamine compounds which are useful as metaldeactivators or metal passivators. Examples include triazole,benzotriazole and substituted benzotriazoles such as alkyl substitutedderivatives. The alkyl substituent generally contains up to 1.5 carbonatoms, preferably up to 8 carbon atoms. The triazoles may contain othersubstituents on the aromatic ring such as halogens, nitro, amino,mercapto, etc. Examples of suitable compounds are benzotriazole and thetolyltriazoles, ethylbenzotriazoles, hexylbenzotriazoles,octylbenzotriazoles, chlorobenzotriazoles and nitrobenzotriazoles.Benzotriazole and tolyltriazole are particularly preferred. A straightor branched chain saturated or unsaturated monocarboxylic acid which isoptionally sulphurised in an amount which may be up to 35% by weight; oran ester of such an acid; and a triazole or alkyl derivatives thereof,or short chain alkyl of up to 5 carbon atoms; n is zero or an integerbetween 1 and 3 inclusive; and is hydrogen, morpholino, alkyl, amido,amino, hydroxy or alkyl or aryl substituted derivatives thereof; or atriazole selected from 1,2,4 triazole, 1,2,3 triazole,5-anilo-1,2,3,4-thiatriazole, 3-amino-1,2,4 triazole,1-H-benzotriazole-1-yl-methylisocyanide, methylene-bis-benzotriazole andnaphthotriazole.

The corrosion inhibitors may be used in an amount of 0.01 to 5 wt %,preferably 0.01 to 1.5 wt %, more preferably 0.01 to 0.2 wt %, stillmore preferably 0.01 to 0.1 wt % (on an as-received basis) based on thetotal weight of the heat transfer fluid composition.

Antifoam Agents

Antifoam agents may advantageously be added to heat transfer fluidcompositions. These agents retard the formation of stable foams.Silicones and organic polymers are typical antifoam agents. For example,polysiloxanes, such as silicon oil or polydimethyl siloxane, provideantifoam properties. Antifoam agents are commercially available and maybe used in conventional minor amounts along with other additives such asdemulsifiers; usually the amount of these additives combined is lessthan 1 weight percent and often less than 0.1 weight percent. In anembodiment, such additives may be used in an amount of about 0.01 to 5weight percent, preferably 0.1 to 3 weight percent, more preferablyabout 0.5 to 1.5 weight percent.

Antiwear Additives

The heat transfer fluid compositions may include at least one antiwearagent. Examples of suitable antiwear agents include oil soluble aminesalts of phosphorus compounds, sulphurized olefins, metaldihydrocarbyldithio-phosphates (such as zinc dialkyldithiophosphates),thiocarbamate-containing compounds, such as thiocarbamate esters,thiocarbamate amides, thiocarbamic ethers, alkylene-coupledthiocarbamates, and bis(S-alkyldithiocarbamyl) disulphides.

Antiwear agents used in the formulation of the heat transfer fluid maybe ashless or ash-forming in nature. Preferably, the antiwear agent isashless. So called ashless antiwear agents are materials that formsubstantially no ash upon combustion. For example, non-metal-containingantiwear agents are considered ashless.

In one embodiment, oil soluble phosphorus amine antiwear agents includean amine salt of a phosphorus acid ester or mixtures thereof. The aminesalt of a phosphorus acid ester includes phosphoric acid esters andamine sails thereof, dialkyldithiophosphoric acid esters and amine saltsthereof, amine salts of phosphites; and amine salts ofphosphorus-containing carboxylic esters, ethers, and amides; andmixtures thereof. The amine salt of a phosphorus acid ester may be usedalone or in combination.

In one embodiment, oil soluble phosphorus amine salts include partialamine salt-partial metal salt compounds or mixtures thereof. In oneembodiment, the phosphorus compound further includes a sulphur atom inthe molecule. In one embodiment, the amine salt of the phosphoruscompound may be ashless, i.e., metal-free (prior to being mixed withother components).

The amines which may be suitable for use as the amine salt includeprimary amines, secondary amines, tertiary amines, and mixtures thereof.The amines include those with at least one hydrocarbyl group, or, incertain embodiments, two or three hydrocarbyl groups. The hydrocarbylgroups may contain 2 to 30 carbon atoms, or in other embodiments 8 to26, or 10 to 20, or 13 to 19 carbon atoms.

Primary amines include ethylamine, propylamine, butylamine,2-ethylhexylamine, octylamine, and dodecylamine, as well as such fattyamines as n-octylamine, n-decylamine, n-dodeclyamine, n-tetradecylamine,n-hexadecylamine, n-octadecylamine and oleyamine. Other useful fattyamines include commercially available fatty amines such as “Armeen™”amines (products available from Akzo Chemicals, Chicago, Ill.), such asArmeen C, Armeen O, Armeen OL, Armeen T, Armeen HT, Armeen S and ArmeenS D, wherein the letter designation relates to the fatty group, such ascoco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dim ethylamine,diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine,diheptylamine, methylethylamine, ethylbutylamine and ethylamylamine. Thesecondary amines may be cyclic amines such as piperidine, piperazine andmorpholine.

The amine may also be a tertiary-aliphatic primary amine. The aliphaticgroup in this case may be an alkyl group containing 2 to 30, or 6 to 26,or 8 to 24 carbon atoms. Tertiary alkyl amines include monoamines suchas tert-butylamine, tert-hexylamine, 1-methyl-1-amino-cyclohexane,tert-octylamine, tert-decylamine, tertdodecylamine,tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine,tert-tetracosanylamine, and tert-octacosanylamine.

In one embodiment, the phosphorus acid amine salt includes an amine withC₁₁ to C₁₄ tertiary alkyl primary groups or mixtures thereof. In oneembodiment, the phosphorus acid amine salt includes an amine with C₁₄ toC₁₈ tertiary alkyl primary amines or mixtures thereof. In oneembodiment, the phosphorus acid amine salt includes an amine with C₁₈ toC₂₂ tertiary alkyl primary amines or mixtures thereof.

Mixtures of amines may also be used in the disclosure. In one embodimenta useful mixture of amines is “Primene™ 81R” and “Primene™ JMT.”Primene™ 81R and Primene™ JMT (both produced and sold by Rohm & Haas)are mixtures of C₁ to C₁₄ tertiary alkyl primary amines and C₁₈ to C₂₂tertiary alkyl primary amines respectively.

In one embodiment, oil soluble amine salts of phosphorus compoundsinclude a sulphur-free amine salt of a phosphorus-containing compoundmay be obtained/obtainable by a process comprising: reacting an aminewith either (i) a hydroxy-substituted di-ester of phosphoric acid, or(ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoricacid. A more detailed description of compounds of this type is disclosedin International Application PCT/US08/051126.

In one embodiment, the hydrocarbyl amine salt of an alkylphosphoric acidester is the reaction product of a C₁₄ to C₁₈ alkylated phosphoric acidwith Primene 81RT™ (produced and sold by Rohm & Haas) which is a mixtureof C₁₁ to C₁₄ tertiary alkyl primary amines.

Examples of hydrocarbyl amine salts of dialkyldithiophosphoric acidesters include the reaction product(s) of isopropyl, methyl-amyl(4-methyl-2-pentyl or mixtures thereof), 2-ethylhexyl, heptyl, octyl ornonyl dithiophosphoric acids with ethylene diamine, morpholine, orPrimene 81R™, and mixtures thereof.

In one embodiment, the dithiophosphoric acid may be reacted with anepoxide or a glycol. This reaction product is further reacted with aphosphorus acid, anhydride, or lower ester. The epoxide includes analiphatic epoxide or a styrene oxide. Examples of useful epoxidesinclude ethylene oxide, propylene oxide, butene oxide, octene oxide,dodecene oxide, and styrene oxide. In one embodiment, the epoxide may bepropylene oxide. The glycols may be aliphatic glycols having from 1 to12, or from 2 to 6, or 2 to 3 carbon atoms. The dithiophosphoric acids,glycols, epoxides, inorganic phosphorus reagents and methods of reactingthe same are described in U.S. Pat. Nos. 3,197,405 and 3,544,465. Theresulting acids may then be salted with amines.

The dithiocarbamate-containing compounds may be prepared by reacting adithiocarbamate acid or salt with an unsaturated compound. Thedithiocarbamate containing compounds may also be prepared bysimultaneously reacting an amine, carbon disulphide and an unsaturatedcompound. Generally, the reaction occurs at a temperature from 25° C. to125° C.

Examples of suitable olefins that may be sulphurised to form thesulphurised olefin include propylene, butylene, isobutylene, pentene,hexane, heptene, octane, nonene, decene, undecene, dodecene, undecyl,tridecene, tetradecene, pentadecene, hexadecene, heptadecene,octadecene, octadecenene, nonodecene, eicosene or mixtures thereof. Inone embodiment, hexadecene, heptadecene, octadecene, octadecenene,nonodecene, eicosene or mixtures thereof and their dimers, trimers andtetramers are especially useful olefins. Alternatively, the olefin maybe a Diels-Alder adduct of a diene such as 1,3-butadiene and anunsaturated ester, such as, butylacrylate.

Another class of sulphurised olefin includes fatty acids and theiresters. The fatty acids are often obtained from vegetable oil or animaloil; and typically contain 4 to 22 carbon atoms. Examples of suitablefatty acids and their esters include triglycerides, oleic acid, linoleicacid, palmitoleic acid or mixtures thereof. Often, the fatty acids areobtained from lard oil, tall oil, peanut oil, soybean oil, cottonseedoil, sunflower seed oil or mixtures thereof. In one embodiment, fattyacids and/or ester are mixed with olefins.

Polyols include diols, triols, and alcohols with higher numbers ofalcoholic OH groups. Polyhydric alcohols include ethylene glycols,including di-, tri- and tetraethylene glycols; propylene glycols,including di-, tri- and tetrapropylene glycols; glycerol; butane diol;hexane diol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose;cyclohexane diol; erythritol; and penta-erythritols, including di- andtripentaerythritol. Often the polyol is diethylene glycol, triethyleneglycol, glycerol, sorbitol, penta erythritol or dipentaerythritol.

In an alternative embodiment, the ashless antiwear agent may be amonoester of a polyol and an aliphatic carboxylic acid, often an acidcontaining 12 to 24 carbon atoms. Often the monoester of a polyol and analiphatic carboxylic acid is in the form of a mixture with a sunfloweroil or the like, which may be present in the mixture from 5 to 95, inseveral embodiments from 10 to 90, or from 20 to 85, or 20 to 80 weightpercent of said mixture. The aliphatic carboxylic acids (especially amonocarboxylic acid) which form the esters are those acids typicallycontaining 12 to 24, or from 14 to 20 carbon atoms. Examples ofcarboxylic acids include dodecanoic acid, stearic acid, lauric acid,behenic acid, and oleic acid.

Illustrative antiwear additives useful in this disclosure include, forexample, metal salts of a carboxylic acid. The metal is selected from atransition metal and mixtures thereof. The carboxylic acid is selectedfrom an aliphatic carboxylic acid, a cycloaliphatic carboxylic acid, anaromatic carboxylic acid, and mixtures thereof.

The metal is preferably selected from a Group 10, 11 and 12 metal, andmixtures thereof. The carboxylic acid is preferably an aliphatic,saturated, unbranched carboxylic acid having from about 8 to about 26carbon atoms, and mixtures thereof.

The metal is preferably selected from nickel (Ni), palladium (Pd),platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), andmixtures thereof.

The carboxylic acid is preferably selected from caprylic acid (C8),pelargonic acid (C9), capric acid (C10), undecylic acid (C11), lauricacid (C12), tridecylic acid (C13), myristic acid (C14), pentadecylicacid (C15), palmitic acid (C16), margaric acid (C17), stearic acid(C18), nonadecylic acid (C19), arachidic acid (C20), heneicosylic acid(C21), behenic acid (C22), tricosylic acid (C23), lignoceric acid (C24),pentacosylic acid (C25), cerotic acid (C26), and mixtures thereof.

Preferably, the metal salt of a carboxylic acid comprises zinc stearate,silver stearate, palladium stearate, zinc palmitate, silver palmitate,palladium palmitate, and mixtures thereof.

The metal salt of a carboxylic acid can be present in the heat transferfluid formulations of this disclosure in an amount of from about 0.01weight percent to about 5 weight percent, based on the total weight ofthe formulated oil.

A metal alkylthiophosphate and more particularly a metal dialkyl dithiophosphate in which the metal constituent is zinc, or zinc dialkyl dithiophosphate (ZDDP) can be a useful component of the heat transfer fluidsof this disclosure. ZDDP can be derived from primary alcohols, secondaryalcohols or mixtures thereof. ZDDP compounds generally are of theformula:

Zn[SP(S)(OR¹)(OR²)]₂

where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups.These alkyl groups may be straight chain or branched. Alcohols used inthe ZDDP can be 2-propanol, butanol, secondary butanol, pentanols,hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethylhexanol, alkylated phenols, and the like. Mixtures of secondary alcoholsor of primary and secondary alcohol can be preferred. Alkyl aryl groupsmay also be used.

Preferable zinc dithiophosphates which are commercially availableinclude secondary zinc dithiophosphates such as those available from forexample, The Lubrizol Corporation under the trade designations “LZ677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite underthe trade designation “OLOA 262” and from for example Afton Chemicalunder the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from about 0.4 weight percentto about 1.2 weight percent, preferably from about 0.5 weight percent toabout 1.0 weight percent, and more preferably from about 0.6 weightpercent to about 0.8 weight percent, based on the total weight of theheat transfer fluid, although more or less can often be usedadvantageously. Preferably, the ZDDP is a secondary ZDDP and present inan amount of from about 0.6 to 1.0 weight percent of the total weight ofthe heat transfer fluid.

Low phosphorus heat transfer fluid formulations are included in thisdisclosure. For such formulations, the phosphorus content is typicallyless than about 0.12 weight percent preferably less than about 0.10weight percent and most preferably less than about 0.085 weight percent.

Other illustrative antiwear agents useful in this disclosure include,for example, zinc alkyldithiophosphates, aryl phosphates and phosphites,sulfur-containing esters, phosphosulfur compounds, and metal or ash-freedithiocarbamates.

The antiwear additive concentration in the heat transfer fluids of thisdisclosure can range from about 0.01 to about 5 weight percent,preferably about 0.1 to 4.5 weight percent, and more preferably fromabout 0.2 weight percent to about 4 weight percent, based on the totalweight of the heat transfer fluid.

Other Additives

The formulated heat transfer fluid useful in the present disclosure mayadditionally contain one or more of the other commonly used heattransfer fluid performance additives including but not limited todispersants, detergents, viscosity modifiers, metal passivators, ionicliquids, extreme pressure additives, anti-seizure agents, wax modifiers,fluid-loss additives, seal compatibility agents, lubricity agents,anti-staining agents, chromophoric agents, defoamants, demulsifiers,emulsifiers, densifiers, wetting agents, gelling agents, tackinessagents, colorants, and others. For a review of many commonly usedadditives, see Klamann in Lubricants and Related Products, VerlagChemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0; see also U.S. Pat.No. 7,704,930, the disclosure of which is incorporated herein in itsentirety. These additives are commonly delivered with varying amounts ofdiluent oil, that may range from 5 weight percent to 50 weight percent.

The additives useful in this disclosure do not have to be soluble in theheat transfer fluids. Insoluble additives such as zinc stearate in oilcan be dispersed in the heat transfer fluids of this disclosure.

The types and quantities of performance additives used in combinationwith the instant disclosure in heat transfer fluid compositions are notlimited by the examples shown herein as illustrations.

Dispersants

The heat transfer fluid compositions may include at least onedispersant. During electrical apparatus component operation,oil-insoluble oxidation byproducts are produced. Dispersants help keepthese byproducts in solution, thus diminishing their deposition on metalsurfaces. Dispersants used in the formulation of the heat transfer fluidmay be ashless or ash-forming in nature. Preferably, the dispersant isashless. So called ashless dispersants are organic materials that formsubstantially no ash upon combustion. For example, non-metal-containingor borated metal-free dispersants are considered ashless.

Suitable dispersants typically contain a polar group attached to arelatively high molecular weight hydrocarbon chain. The polar grouptypically contains at least one element of nitrogen, oxygen, orphosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the (poly)alkenylsuccinicderivatives, typically produced by the reaction of a long chainhydrocarbyl substituted succinic compound, usually a hydrocarbylsubstituted succinic anhydride, with a polyhydroxy or polyaminocompound. The long chain hydrocarbyl group constituting the oleophilicportion of the molecule which confers solubility in the oil, is normallya polyisobutylene group. Many examples of this type of dispersant arewell known commercially and in the literature. Exemplary U.S. patentsdescribing such dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707;3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012;3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersantare described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025;3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574;3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250;3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. Afurther description of dispersants may be found, for example, inEuropean Patent Application No. 471 071, to which reference is made forthis purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substitutedsuccinic anhydride derivatives are useful dispersants. In particular,succinimide, succinate esters, or succinate ester amides prepared by thereaction of a hydrocarbon-substituted succinic acid compound preferablyhaving at least 50 carbon atoms in the hydrocarbon substituent, with atleast one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbylsubstituted succinic anhydrides and amines. Molar ratios can varydepending on the polyamine. For example, the molar ratio of hydrocarbylsubstituted succinic anhydride to TEPA can vary from about 1:1 to about5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936;3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800.

Succinate esters are formed by the condensation reaction betweenhydrocarbyl substituted succinic anhydrides and alcohols or polyols.Molar ratios can vary depending on the alcohol or polyol used. Forexample, the condensation product of a hydrocarbyl substituted succinicanhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction betweenhydrocarbyl substituted succinic anhydrides and alkanol amines. Forexample, suitable alkanol amines include ethoxylatedpolyalkylpolyamines, propoxylated polyalkylpolyamines andpolyalkenylpolyamines such as polyethylene polyamines. One example ispropoxylated hexamethylenediamine. Representative examples are shown inU.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydridesused in the preceding paragraphs will typically range between 800 and2,500 or more. The above products can be post-reacted with variousreagents such as sulfur, oxygen, formaldehyde, carboxylic acids such asoleic acid. The above products can also be post reacted with boroncompounds such as boric acid, borate esters or highly borateddispersants, to form borated dispersants generally having from about 0.1to about 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols,formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which isincorporated herein by reference. Process aids and catalysts, such asoleic acid and sulfonic acids, can also be part of the reaction mixture.Molecular weights of the alkylphenols range from 800 to 2,500.Representative examples are shown in U.S. Pat. Nos. 3,697,574;3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannichcondensation products useful in this disclosure can be prepared fromhigh molecular weight alkyl-substituted hydroxyaromatics or HNR₂group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are wellknown to one skilled in the art; see, for example, U.S. Pat. Nos.3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Illustrative dispersants include borated and non-borated succinimides,including those derivatives from mono-succinimides, bis-succinimides,and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbylsuccinimide is derived from a hydrocarbylene group such aspolyisobutylene having a Mn of from about 500 to about 5000, or fromabout 1000 to about 3000, or about 1000 to about 2000, or a mixture ofsuch hydrocarbylene groups, often with high terminal vinylic groups.Other preferred dispersants include succinic acid-esters and amides,alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives,and other related components.

Polymethacrylate or polyacrylate derivatives are another class ofdispersants. These dispersants are typically prepared by reacting anitrogen containing monomer and a methacrylic or acrylic acid esterscontaining 5-25 carbon atoms in the ester group. Representative examplesare shown in U.S. Pat. Nos. 2,100,993, and 6,323,164. Polymethacrylateand polyacrylate dispersants are normally used as multifunctionalviscosity modifiers. The lower molecular weight versions can be used asheat transfer fluid dispersants or fuel detergents.

Other illustrative dispersants useful in this disclosure include thosederived from polyalkenyl-substituted mono- or dicarboxylic acid,anhydride or ester, which dispersant has a polyalkenyl moiety with anumber average molecular weight of at least 900 and from greater than1.3 to 1.7, preferably from greater than 1.3 to 1.6, most preferablyfrom greater than 1.3 to 1.5, functional groups (mono- or dicarboxylicacid producing moieties) per polyalkenyl moiety (a medium functionalitydispersant). Functionality (F) can be determined according to thefollowing formula:

F=(SAP×M _(n))/((112,200×A.I.)−(SAP×98))

wherein SAP is the saponification number (i.e., the number of milligramsof KOH consumed in the complete neutralization of the acid groups in onegram of the succinic-containing reaction product, as determinedaccording to ASTM D94); M_(n) is the number average molecular weight ofthe starting olefin polymer; and A.I. is the percent active ingredientof the succinic-containing reaction product (the remainder beingunreacted olefin polymer, succinic anhydride and diluent).

The polyalkenyl moiety of the dispersant may have a number averagemolecular weight of at least 900, suitably at least 1500, preferablybetween 1800 and 3000, such as between 2000 and 2800, more preferablyfrom about 2100 to 2500, and most preferably from about 2200 to about2400. The molecular weight of a dispersant is generally expressed interms of the molecular weight of the polyalkenyl moiety. This is becausethe precise molecular weight range of the dispersant depends on numerousparameters including the type of polymer used to derive the dispersant,the number of functional groups, and the type of nucleophilic groupemployed.

Polymer molecular weight, specifically Mn, can be determined by variousknown techniques. One convenient method is gel permeation chromatography(GPC), which additionally provides molecular weight distributioninformation (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern SizeExclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979).Another useful method for determining molecular weight, particularly forlower molecular weight polymers, is vapor pressure osmometry (e.g., ASTMD3592).

The polyalkenyl moiety in a dispersant preferably has a narrow molecularweight distribution (MWD), also referred to as polydispersity, asdetermined by the ratio of weight average molecular weight (Mw) tonumber average molecular weight (Ma). Polymers having a Mw/M_(n) of lessthan 2.2, preferably less than 2.0, are most desirable. Suitablepolymers have a polydispersity of from about 1.5 to 2.1, preferably fromabout 1.6 to about 1.8.

Suitable polyalkenes employed in the formation of the dispersantsinclude homopolymers, interpolymers or lower molecular weighthydrocarbons. One family of such polymers comprise polymers of ethyleneand/or at least one C₃ to C₂₄ alpha-olefin. Preferably, such polymerscomprise interpolymers of ethylene and at least one alpha-olefin of theabove formula.

Another useful class of polymers is polymers prepared by cationicpolymerization of monomers such as isobutene and styrene. Commonpolymers from this class include polyisobutenes obtained bypolymerization of a C₄ refinery stream having a butene content of 35 to75% by wt., and an isobutene content of 30 to 60% by wt. A preferredsource of monomer for making poly-n-butenes is petroleum feedstreamssuch as Raffinate II. These feedstocks are disclosed in the art such asin U.S. Pat. No. 4,952,739. A preferred embodiment utilizespolyisobutylene prepared from a pure isobutylene stream or a Raffinate Istream to prepare reactive isobutylene polymers with terminal vinylideneolefins. Polyisobutene polymers that may be employed are generally basedon a polymer chain of from 1500 to 3000.

Dispersants that contain the alkenyl or alkyl group have an Mn value ofabout 500 to about 5000 and an Mw/Mn ratio of about 1 to about 5. Thepreferred Mn intervals depend on the chemical nature of the agentimproving filterability. Polyolefinic polymers suitable for the reactionwith maleic anhydride or other acid materials or acid forming materials,include polymers containing a predominant quantity of C₂ to C₅monoolefins, for example, ethylene, propylene, butylene, isobutylene andpentene. A highly suitable polyolefinic polymer is polyisobutene. Thesuccinic anhydride preferred as a reaction substance is PIBSA, that is,polyisobutenyl succinic anhydride.

If the dispersant contains a succinimide comprising the reaction productof a succinic anhydride with a polyamine, the alkenyl or alkylsubstituent of the succinic anhydride serving as the reaction substanceconsists preferably of polymerised isobutene having an Mn value of about1200 to about 2500. More advantageously, the alkenyl or alkylsubstituent of the succinic anhydride serving as the reaction substanceconsists in a polymerised isobutene having an Mn value of about 2100 toabout 2400. If the agent improving filterability contains an ester ofsuccinic acid comprising the reaction product of a succinic anhydrideand an aliphatic polyhydric alcohol, the alkenyl or alkyl substituent ofthe succinic anhydride serving as the reaction substance consistsadvantageously of a polymerised isobutene having an Mn value of 500 to1500. In preference, a polymerised isobutene having an Mn value of 850to 1200 is used.

The amides may be amides of mono- or polycarboxylic acids or reactivederivatives thereof. The amides may be characterized by a hydrocarbylgroup containing from about 6 to about 90 carbon atoms; each isindependently hydrogen or a hydrocarbyl, aminohydrocarbyl,hydroxyhydrocarbyl or a heterocyclic-substituted hydrocarbyl group,provided that both are not hydrogen; each is, independently, ahydrocarbylene group containing up to about 10 carbon atoms.

The amide can be derived from a monocarboxylic acid, a hydrocarbyl groupcontaining from 6 to about 30 or 38 carbon atoms and more often will bea hydrocarbyl group derived from a fatty acid containing from 12 toabout 24 carbon atoms.

An illustrative amide that is derived from a di- or tricarboxylic acid,will contain from 6 to about 90 or more carbon atoms depending on thetype of polycarboxylic acid. For example, when the amide is derived froma dimer acid, will contain from about 18 to about 44 carbon atoms ormore, and amides derived from trimer acids generally will contain anaverage of from about 44 to about 90 carbon atoms. Each is independentlyhydrogen or a hydrocarbyl, aminohydrocarbyl, hydroxyhydrocarbyl or aheterocyclic-substituted hydrocarbon group containing up to about 10carbon atoms. It may be independently heterocyclic substitutedhydrocarbyl groups wherein the heterocyclic substituent is derived frompyrrole, pyrroline, pyrrolidine, morpholine, piperazine, piperidine,pyridine, pipecoline, etc. Specific examples include methyl, ethyl,n-propyl, n-butyl, n-hexyl, hydroxymethyl, hydroxyethyl, hydroxypropyl,amino-methyl, aminoethyl, aminopropyl, 2-ethylpyridine,1-ethylpyrrolidine, 1-ethylpiperidine, etc.

Illustrative aliphatic monoamines include mono-aliphatic anddi-aliphatic-substituted amines wherein the aliphatic groups may besaturated or unsaturated and straight chain or branched chain. Suchamines include, for example, mono- and di-alkyl-substituted amines,mono- and dialkenyl-substituted amines, etc. Specific examples of suchmonoamines include ethyl amine, diethyl amine, n-butyl amine, di-n-butylamine, isobutyl amine, coco amine, stearyl amine, oleyl amine, etc. Anexample of a cycloaliphatic-substituted aliphatic amine is2-(cyclohexyl)-ethyl amine. Examples of heterocyclic-substitutedaliphatic amines include 2-(2-aminoethyl)-pyrrole,2-(2-aminoethyl)-1-methylpyrrole, 2-(2-aminoethyl)-1-methylpyrrolidineand 4-(2-aminoethyl)morpholine, 1-(2-aminoethyl)piperazine,1-(2-aminoethyl)piperidine, 2-(2-aminoethyl)pyridine,1-(2-aminoethyl)pyrrolidine, 1-(3-aminopropyl)imidazole,3-(2-aminopropyl)indole, 4-(3-aminopropyl)morpholine,1-(3-aminopropyl)-2-pipecoline, 1-(3-aminopropyl)-2-pyrrolidinone, etc.

Illustrative cycloaliphatic monoamines are those monoamines whereinthere is one cycloaliphatic substituent attached directly to the aminonitrogen through a carbon atom in the cyclic ring structure. Examples ofcycloaliphatic monoamines include cyclohexylamines, cyclopentylamines,cyclohexenylamines, cyclopentenylamines, N-ethyl-cyclohexylamine,dicyclohexylamines, and the like. Examples of aliphatic-substituted,aromatic-substituted, and heterocyclic-substituted cycloaliphaticmonoamines include propyl-substituted cyclohexylamines,phenyl-substituted cyclopentylamines, and pyranyl-substitutedcyclohexylamine.

Illustrative aromatic amines include those monoamines wherein a carbonatom of the aromatic ring structure is attached directly to the aminonitrogen. The aromatic ring will usually be a mononuclear aromatic ring(i.e., one derived from benzene) but can include fused aromatic rings,especially those derived from naphthalene. Examples of aromaticmonoamines include aniline, di-(para-methylphenyl)amine, naphthylamine,N-(n-butyl)-aniline, and the like. Examples of aliphatic-substituted,cycloaliphatic-substituted, and heterocyclic-substituted aromaticmonoamines are para-ethoxy-aniline, para-dodecylaniline,cyclohexyl-substituted naphthylamine, variously substitutedphenathiazines, and thienyl-substituted aniline.

Illustrative polyamines are aliphatic, cycloaliphatic and aromaticpolyamines analogous to the above-described monoamines except for thepresence within their structure of additional amino nitrogens. Theadditional amino nitrogens can be primary, secondary or tertiary aminonitrogens. Examples of such polyamines includeN-amino-propyl-cyclohexylamines, N,N′-di-n-butyl-paraphenylene diamine,bis-(para-aminophenyl)methane, 1,4-diaminocyclohexane, and the like.

Illustrative hydroxy-substituted amines are those having hydroxysubstituents bonded directly to a carbon atom other than a carbonylcarbon atom; that is, they have hydroxy groups capable of functioning asalcohols. Examples of such hydroxy-substituted amines includeethanolamine, di-(3-hydroxypropyl)-amine, 3-hydroxybutyl-amine,4-hydroxybutyl-amine, diethanolamine, di-(2-hydroxyamine,N-(hydroxypropyl)-propylamine, N-(2-methyl)-cyclohexylamine,3-hydroxycyclopentyl parahydroxyaniline, N-hydroxyethal piperazine andthe like.

In one embodiment, the amines are alkylene polyamines includinghydrogen, or a hydrocarbyl, amino hydrocarbyl, hydroxyhydrocarbyl orheterocyclic-substituted hydrocarbyl group containing up to about 10carbon atoms. Examples of such alkylene polyamines include methylenepolyamines, ethylene polyamines, butylene polyamines, propylenepolyamines, pentylene polyamines, hexylene polyamines, heptylenepolyamines, etc.

Alkylene polyamines include ethylene diamine, triethylene tetramine,propylene diamine, trimethylene diamine, hexamethylene diamine,decamethylene diamine, hexamethylene diamine, decamethylene diamine,octamethylene diamine, di(heptamethylene) triamine, tripropylenetetramine, tetraethylene pentamine, trimethylene diamine, pentaethylenehexamine, di(trimethylene)triamine, and the like. Higher homologs as areobtained by condensing two or more of the above-illustrated alkyleneamines are useful, as are mixtures of two or more of any of theafore-described polyamines.

Ethylene polyamines, such as those mentioned above, are especiallyuseful for reasons of cost and effectiveness. Such polyamines aredescribed in detail under the heading “Diamines and Higher Amines” inThe Encyclopedia of Chemical Technology, Second Edition, Kirk andOthmer, Volume 7, pages 27-39, Interscience Publishers, Division of JohnWiley and Sons, 1965, which is hereby incorporated by reference for thedisclosure of useful polyamines. Such compounds are prepared mostconveniently by the reaction of an alkylene chloride with ammonia or byreaction of an ethylene imine with a ring-opening reagent such asammonia, etc. These reactions result in the production of the somewhatcomplex mixtures of alkylene polyamines, including cyclic condensationproducts such as piperazines.

Other useful types of polyamine mixtures are those resulting fromstripping of the above-described polyamine mixtures. In this instance,lower molecular weight polyamines and volatile contaminants are removedfrom an alkylene polyamine mixture to leave as residue what is oftentermed “polyamine bottoms”. In general, alkylene polyamine bottoms canbe characterized as having less than 2, usually less than 1% (by weight)material boiling below about 200° C. In the instance of ethylenepolyamine bottoms, which are readily available and found to be quiteuseful, the bottoms contain less than about 2% (by weight) totaldiethylene triamine (DETA) or triethylene tetramine (TETA). A typicalsample of such ethylene polyamine bottoms obtained from the Dow ChemicalCompany of Freeport, Tex. designated “E-100”. Gas chromatographyanalysis of such a sample showed it to contain about 0.93% “Light Ends”(most probably DETA), 0.72% TETA, 21.74% tetraethylene pentamine and76.61% pentaethylene hexamine and higher (by weight). These alkylenepolyamine bottoms include cyclic condensation products such aspiperazine and higher analogs of diethylene triamine, triethylenetetramine and the like.

Illustrative dispersants are selected from: Mannich bases that arecondensation reaction products of a high molecular weight phenol, analkylene polyamine and an aldehyde such as formaldehyde; succinic-baseddispersants that are reaction products of a olefin polymer and succinicacylating agent (acid, anhydride, ester or halide) further reacted withan organic hydroxy compound and/or an amine; high molecular weightamides and esters such as reaction products of a hydrocarbyl acylatingagent and a polyhydric aliphatic alcohol (such as glycerol,pentaerythritol or sorbitol). Ashless (metal-free) polymeric materialsthat usually contain an oil soluble high molecular weight backbonelinked to a polar functional group that associates with particles to bedispersed are typically used as dispersants. Zinc acetate capped, alsoany treated dispersant, which include borated, cyclic carbonate,end-capped, polyalkylene maleic anhydride and the like; mixtures of someof the above, in treat rates that range from about 0.1% up to 10-20% ormore. Commonly used hydrocarbon backbone materials are olefin polymersand copolymers, i.e., ethylene, propylene, butylene, isobutylene,styrene; there may or may not be further functional groups incorporatedinto the backbone of the polymer, whose molecular weight ranges from 300tp to 5000. Polar materials such as amines, alcohols, amides or estersare attached to the backbone via a bridge.

The dispersant(s) are preferably non-polymeric (e.g., mono- orbis-succinimides). Such dispersants can be prepared by conventionalprocesses such as disclosed in U.S. Patent Application Publication No.2008/0020950, the disclosure of which is incorporated herein byreference.

The dispersant(s) can be borated by conventional means, as generallydisclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.

Such dispersants may be used in an amount of about 0.01 to 20 weightpercent or 0.01 to 10 weight percent, preferably about 0.5 to 8 weightpercent, or more preferably 0.5 to 4 weight percent. Or such dispersantsmay be used in an amount of about 2 to 12 weight percent, preferablyabout 4 to 10 weight percent, or more preferably 6 to 9 weight percent.On an active ingredient basis, such additives may be used in an amountof about 0.06 to 14 weight percent, preferably about 0.3 to 6 weightpercent. The hydrocarbon portion of the dispersant atoms can range fromC₆₀ to C₁₀₀₀, or from C₇₀ to C₃₀₀, or from C₇₀ to C₂₀₀. Thesedispersants may contain both neutral and basic nitrogen, and mixtures ofboth. Dispersants can be end-capped by borates and/or cyclic carbonates.Nitrogen content in the finished oil can vary from about 200 ppm byweight to about 2000 ppm by weight, preferably from about 200 ppm byweight to about 1200 ppm by weight. Basic nitrogen can vary from about100 ppm by weight to about 1000 ppm by weight, preferably from about 100ppm by weight to about 600 ppm by weight.

As used herein, the dispersant concentrations are given on an “asdelivered” basis. Typically, the active dispersant is delivered with aprocess oil. The “as delivered” dispersant typically contains from about20 weight percent to about 80 weight percent, or from about 40 weightpercent to about 60 weight percent, of active dispersant in the “asdelivered” dispersant product.

Detergents

The heat transfer fluid compositions may include at least one detergent.Illustrative detergents useful in this disclosure include, for example,alkali metal detergents, alkaline earth metal detergents, or mixtures ofone or more alkali metal detergents and one or more alkaline earth metaldetergents. A typical detergent is an anionic material that contains along chain hydrophobic portion of the molecule and a smaller anionic oroleophobic hydrophilic portion of the molecule. The anionic portion ofthe detergent is typically derived from an organic acid such as a sulfuracid, carboxylic acid (e.g., salicylic acid), phosphorous acid, phenol,or mixtures thereof. The counterion is typically an alkaline earth oralkali metal.

The detergent is preferably a metal salt of an organic or inorganicacid, a metal salt of a phenol, or mixtures thereof. The metal ispreferably selected from an alkali metal, an alkaline earth metal, andmixtures thereof. The organic or inorganic acid is selected from analiphatic organic or inorganic acid, a cycloaliphatic organic orinorganic acid, an aromatic organic or inorganic acid, and mixturesthereof.

The metal is preferably selected from an alkali metal, an alkaline earthmetal, and mixtures thereof. More preferably, the metal is selected fromcalcium (Ca), magnesium (Mg), and mixtures thereof.

The organic acid or inorganic acid is preferably selected from a sulfuracid, a carboxylic acid, a phosphorus acid, and mixtures thereof.

Preferably, the metal salt of an organic or inorganic acid or the metalsalt of a phenol comprises calcium phenate, calcium sulfonate, calciumsalicylate, magnesium phenate, magnesium sulfonate, magnesiumsalicylate, and mixtures thereof.

Salts that contain a substantially stochiometric amount of the metal aredescribed as neutral salts and have a total base number (TBN, asmeasured by ASTM D2896) of from 0 to 80. Many compositions areoverbased, containing large amounts of a metal base that is achieved byreacting an excess of a metal compound (a metal hydroxide or oxide, forexample) with an acidic gas (such as carbon dioxide). Useful detergentscan be neutral, mildly overbased, or highly overbased. These detergentscan be used in mixtures of neutral, overbased, highly overbased calciumsalicylate, sulfonates, phenates and/or magnesium salicylate,sulfonates, phenates. The TBN ranges can vary from low, medium to highTBN products, including as low as 0 to as high as 600. Preferably, theTBN delivered by the detergent is between 1 and 20. More preferablybetween 1 and 12. Mixtures of low, medium, high TBN can be used, alongwith mixtures of calcium and magnesium metal based detergents, andincluding sulfonates, phenates, salicylates, and carboxylates. Adetergent mixture with a metal ratio of 1, in conjunction of a detergentwith a metal ratio of 2, and as high as a detergent with a metal ratioof 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. Thesedetergents can be made by reacting alkaline earth metal hydroxide oroxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with analkyl phenol or sulfurized alkylphenol. Useful alkyl groups includestraight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ ormixtures thereof. Examples of suitable phenols include isobutylphenol,2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It shouldbe noted that starting alkylphenols may contain more than one alkylsubstituent that are each independently straight chain or branched andcan be used from 0.5 to 6 weight percent. When a non-sulfurizedalkylphenol is used, the sulfurized product may be obtained by methodswell known in the art. These methods include heating a mixture ofalkylphenol and sulfurizing agent (including elemental sulfur, sulfurhalides such as sulfur dichloride, and the like) and then reacting thesulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are useful detergents. These carboxylicacid detergents may be prepared by reacting a basic metal compound withat least one carboxylic acid and removing free water from the reactionproduct. Detergents made from salicylic acid are one preferred class ofdetergents derived from carboxylic acids. Useful salicylates includelong chain alkyl salicylates. One useful family of compositions is ofthe formula

where R is an alkyl group having 1 to about 30 carbon atoms, n is aninteger from 1 to 4, and M is an alkaline earth metal. Preferred Rgroups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. Rmay be optionally substituted with substituents that do not interferewith the detergent's function. M is preferably, calcium, magnesium, orbarium. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols bythe Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of thehydrocarbyl-substituted salicylic acids may be prepared by doubledecomposition of a metal salt in a polar solvent such as water oralcohol.

Alkaline earth metal phosphates are also used as detergents and areknown in the art.

Detergents may be simple detergents or what is known as hybrid orcomplex detergents. The latter detergents can provide the properties oftwo detergents without the need to blend separate materials. See U.S.Pat. No. 6,034,039.

Illustrative detergents include calcium alkylsalicylates, calciumalkylphenates and calcium alkarylsulfonates with alternate metal ionsused such as magnesium, barium, or sodium. Examples of the cleaning anddispersing agents that can be used include metal-based detergents suchas the neutral and basic alkaline earth metal sulphonates, alkalineearth metal phenates and alkaline earth metal salicylatesalkenylsuccinimide and alkenylsuccinimide esters and their borohydrides,phenates, salienius complex detergents and ashless dispersing agentswhich have been modified with sulphur compounds. These agents can beadded and used individually or in the form of mixtures, conveniently inan amount within the range of from 0.01 to 1 part by weight per 100parts by weight of base oil; these can also be high TBN, low TBN, ormixtures of high/low TBN.

Preferred detergents include calcium sulfonates, magnesium sulfonates,calcium salicylates, magnesium salicylates, calcium phenates, magnesiumphenates, and other related components (including borated detergents),and mixtures thereof. Preferred mixtures of detergents include magnesiumsulfonate and calcium salicylate, magnesium sulfonate and calciumsulfonate, magnesium sulfonate and calcium phenate, calcium phenate andcalcium salicylate, calcium phenate and calcium sulfonate, calciumphenate and magnesium salicylate, calcium phenate and magnesium phenate.

The detergent concentration in the heat transfer fluids of thisdisclosure can range from about 0.01 to about 10 weight percent,preferably about 0.1 to 7.5 weight percent, and more preferably fromabout 0.5 weight percent to about 5 weight percent, based on the totalweight of the heat transfer fluid.

As used herein, the detergent concentrations are given on an “asdelivered” basis. Typically, the active detergent is delivered with aprocess oil. The “as delivered” detergent typically contains from about20 weight percent to about 100 weight percent, or from about 40 weightpercent to about 60 weight percent, of active detergent in the “asdelivered” detergent product.

Viscosity Modifiers

Viscosity modifiers (also known as viscosity index improvers (VIimprovers), and viscosity improvers) can be included in the heattransfer fluid compositions of this disclosure.

Viscosity modifiers provide heat transfer fluids with high and lowtemperature operability. These additives impart shear stability atelevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity modifiers include high molecular weight hydrocarbons,polyesters and viscosity modifier dispersants that function as both aviscosity modifier and a dispersant. Typical molecular weights of thesepolymers are between about 10,000 to 1,500,000, more typically about20,000 to 1,200,000, and even more typically between about 50,000 and1,000,000.

Examples of suitable viscosity modifiers are linear or star-shapedpolymers and copolymers of methacrylate, butadiene, olefins, oralkylated styrenes. Polyisobutylene is a commonly used viscositymodifier. Another suitable viscosity modifier is polymethacrylate(copolymers of various chain length alkyl methacrylates, for example),some formulations of which also serve as pour point depressants. Othersuitable viscosity modifiers include copolymers of ethylene andpropylene, hydrogenated block copolymers of styrene and isoprene, andpolyacrylates (copolymers of various chain length acrylates, forexample). Specific examples include styrene-isoprene orstyrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers are commercially available from Chevron OroniteCompany LLC under the trade designation “PARATONE®” (such as “PARATONE®8921” and “PARATONE® 8941”); from Afton Chemical Corporation under thetrade designation “HiTEC®” (such as “HiTEC® 5850B”; and from TheLubrizol Corporation under the trade designation “Lubrizol® 7067C”.Hydrogenated polyisoprene star polymers are commercially available fromInfineum International Limited, e.g., under the trade designation“SV200” and “SV600”. Hydrogenated diene-styrene block copolymers arecommercially available from Infineum International Limited, e.g., underthe trade designation “SV 50”.

The polymethacrylate or polyacrylate polymers can be linear polymerswhich are available from Evnoik Industries under the trade designation“Viscoplex®” (e.g., Viscoplex 6-954) or star polymers which areavailable from Lubrizol Corporation under the trade designation Asteric™(e.g., Lubrizol 87708 and Lubrizol 87725).

Illustrative vinyl aromatic-containing polymers useful in thisdisclosure may be derived predominantly from vinyl aromatic hydrocarbonmonomer. Illustrative vinyl aromatic-containing copolymers useful inthis disclosure may be represented by the following general formula:

A-B

wherein A is a polymeric block derived predominantly from vinyl aromatichydrocarbon monomer, and B is a polymeric block derived predominantlyfrom conjugated diene monomer.

In an embodiment of this disclosure, the viscosity modifiers may be usedin an amount of less than about 10 weight percent, preferably less thanabout 7 weight percent, more preferably less than about 4 weightpercent, and in certain instances, may be used at less than 2 weightpercent, preferably less than about 1 weight percent, and morepreferably less than about 0.5 weight percent, based on the total weightof the formulated heat transfer fluid. Viscosity modifiers are typicallyadded as concentrates, in large amounts of diluent oil.

The viscosity modifiers may be used in an amount of 0.01 to 20 wt %,preferably 0.1 to 10 wt %, more preferably 0.5 to 7.5 wt %, still morepreferably 1 to 5 wt % (on an as-received basis) based on the totalweight of the heat transfer fluid composition.

As used herein, the viscosity modifier concentrations are given on an“as delivered” basis. Typically, the active polymer is delivered with adiluent oil. The “as delivered” viscosity modifier typically containsfrom 20 weight percent to 75 weight percent of an active polymer forpolymethacrylate or polyacrylate polymers, or from 8 weight percent to20 weight percent of an active polymer for olefin copolymers,hydrogenated polyisoprene star polymers, or hydrogenated diene-styreneblock copolymers, in the “as delivered” polymer concentrate.

Metal Passivators

The heat transfer fluid compositions may include at least one metalpassivator. The metal passivators/deactivators include, for example,benzotriazole, tolyltriazole, 2-mercaptobenzothiazole,dialkyl-2,5-dimercapto-1,3,4-thiadiazole;N,N′-disalicylideneethylenediamine,N,N′-disalicyli-denepropylenediamine; zinc dialkyldithiophosphates anddialkyl dithiocarbamates.

Some embodiments of the disclosure may further comprise a yellow metalpassivator. As used herein, “yellow metal” refers to a metallurgicalgrouping that includes brass and bronze alloys, aluminum bronze,phosphor bronze, copper, copper nickel alloys, and beryllium copper.Typical yellow metal passivators include, for example, benzotriazole,totutriazole, tolyltriazole, mixtures of sodium tolutriazole andtolyltriazole, and combinations thereof. In one particular andnon-limiting embodiment, a compound containing tolyltriazole isselected. Typical commercial yellow metal passivators includeIRGAMET™-30, and IRGAMET™-42, available from Ciba Specialty Chemicals,now part of BASE, and VANLUBE™ 601 and 704, and CUVAN™ 303 and 484,available from R.T. Vanderbilt Company, Inc.

The metal passivator concentration in the heat transfer fluids of thisdisclosure can range from about 0.01 to about 5.0 weight percent,preferably about 0.01 to 3.0 weight percent, and more preferably fromabout 0.01 weight percent to about 1.5 weight percent, based on thetotal weight of the heat transfer fluid.

Ionic Liquids (ILs)

Ionic liquids are so-called salt melts that are preferably liquid atroom temperature and/or by definition have a melting point <100° C. Theyhave almost no vapor pressure and therefore have no cavitationproperties. In addition, through the choice of the cations and anions inthe ionic liquids, the lifetime of the heat transfer fluid is increased,and by adjusting the electric conductivity, these liquids can be used inequipment in which there is an electric charge buildup, e.g., electricvehicle components. Suitable cations for ionic liquids include aquaternary ammonium cation, a phosphonium cation, an imidazolium cation,a pyridinium cation, a pyrazolium cation, an oxazolium cation, apyrrolidinium cation, a piperidinium cation, a thiazolium cation, aguanidinium cation, a morpholinium cation, a trialkylsulfonium cation ora triazolium cation, which may be substituted with an anion selectedfrom the group consisting of [PF₆]⁻, [BF₄]³¹, [CF₃CO₂]³¹, [CF₃SO₃]⁻ aswell as its higher homologs, [C₄F₉—SO₃]³¹ or [C₈F₁₇—SO₃]⁻ and higherperfluoroalkylsulfonates, [(CF₃SO₂)₂N]⁻, [(CF₃SO₂)(CF₃COO)N]⁻,[R¹—SO₃]⁻, [R¹—O—SO₃]³¹, [R¹—COO]⁻, Cr⁻, Br⁻, [NO₃]⁻, [N(CN)₂]⁻,[HSO₄]⁻, PF_((6-x))R³ _(x) or [R¹R²PO₄]⁻ and the radicals R¹ and R²independently of one another are selected from hydrogen; linear orbranched, saturated or unsaturated, aliphatic or alicyclic alkyl groupswith 1 to 20 carbon atoms; heteroaryl, heteroaryl-C₁-C₆-alkyl groupswith 3 to 8 carbon atoms in the heteroaryl radical and at least oneheteroatom of N, O and S, which may be combined with at least one groupselected from C₁-C₆ alkyl groups and/or halogen atoms; aryl-aryl C₁-C₆alkyl groups with 5 to 12 carbon atoms in the aryl radical, which may besubstituted with at least one C₁-C₆ alkyl group; R³ may be aperfluoroethyl group or a higher perfluoroalkyl group, x is 1 to 4.However, other combinations are also possible.

Ionic liquids with highly fluorinated anions are especially preferredbecause they usually have a high thermal stability. The water uptakeability may definitely be reduced by such anions, e.g., in the case ofthe bis(trifluoromethylsutfonyl)imide anion.

Illustrative ionic liquids include, for example,butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MBPimide),methylpropylpyrrolidinium bis(trifluoromethylsulfonyl)imide (MPPimide),hexylmethylimidazolium tris(perfluoroethyl)trifluorophosphate(HMIMPFET), hexylmethylimidazolium bis(trifluoromethylsulfonyl)imide(HMIMimide), hexylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide(HMP), tetrabutylphosphonium tris(perfluoroethyl)trifluorophosphate(BuPPFET), octylmethylimidazolium hexafluorophosphate (OMIM PF6),hexylpyridinium bis(trifluoromethyl)sulfonylimide (Hpyimide),methyltrioctylammonium trifluoroacetate (MOAac),butylmethylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate(MBPPFET), trihexyl(tetradecyl)phosphoniumbis(trifluoromethylsulfonyl)imide (HPDimide),1-ethyl-3-methylimidazolium ethyl sulfate (EMIM ethyl sulfate),1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(EMIMimide), 1-ethyl-2,3-dimethylimidazoliumbis(trifluoromethylsulfonyl)imide (EMMIMimide),N-ethyl-3-methylpyridinium nonafluorobutanesulfonate (EMPyflate),trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide,trihexyl(tetradecyl)phosphoniumbis(2,4,4-trifluoromethylpentyl)phosphinate,tributyl(tetradecyl)phosphonium dodecylbenzenesulfonate, and the like.

Cation/anion combinations leading to ionic liquids include, for example,dialkylimidazolium, pyridinium, ammonium and phosphonium, etc. withorganic anions such as sulfonates, imides, methides, etc., as well asinorganic anions such as halides and phosphates, etc., such that anyother combination of cations and anions with which a low melting pointcan be achieved is also conceivable. Ionic liquids have an extremely lowvapor pressure, depending on their chemical structure, are nonflammableand often have thermal stability up to more than 260° C. and furthermoreare also suitable as heat transfer fluids.

The respective desired properties of the heat transfer fluids areachieved with the ionic liquids through a suitable choice of cations andanions. These desirable properties include adjusting electricalconductivity of the heat transfer fluid to spread the area of use,increasing the service life of the heat transfer fluid, and adjustingthe viscosity to improve the temperature suitability. Suitable cationsfor ionic liquids have proven to be a phosphonium cation, an imidazoliumcation, a pyridinium cation or a pyrrolidinium cation which may becombined with an anion containing fluorine and selected frombis(trifluoromethylsulfonyl)imide, bis(perfluoroalkylsulfonyl)imide,perfluoroalkyl sulfonate, tris(perfluoroalkyl)methidenes,bis(perfluoroalkyl)imidenes, bis(perfluoroaryl)imides,perfluoroarylperfluoroalkylsulfonylimides and tris(perfluoro-alkyl)trifluorophosphate or with a halogen-free alkyl sulfate anion.

Ionic liquids are preferred with highly fluorinated anions because theyusually have a high thermal stability. The water uptake ability may bereduced significantly by such anions, e.g., when usingbis(trifluoromethylsulfonyl) anion.

In an embodiment, such ionic liquid additives may be used in an amountof about 0.1 to 10 weight percent, preferably 0.5 to 7.5 weight percent,more preferably about 0.75 to 5 weight percent.

Antistatic Additives

In electrical apparatus components, static electricity is generated,especially when the heat transfer fluid is in use. To reduce thathazard, a conductive antistatic additive can be added to and distributedthroughout the heat transfer fluid. This heat transfer fluid willthereby avoid reduction in its performance associated with localbreakdown of the base stock and safety problems from static electricbuild-up.

A class of products called “antistatic fluids” or “antistaticadditives”, which also are petroleum distillates, can be added to adjustthe conductivity of a heat transfer fluid to safe levels, e.g., at orabove 100 pico-siemens per meter conductivity. Very small quantities ofthese antistatic fluids are required to raise the conductivity to thedesired levels, namely, some 10 to 30 milliliters per 1,000 gallons ofhydrocarbon.

According to another feature of the disclosure, the antistatic additiveis selected from a population of commercially available materials basedon the ability of the material's chemical compatibility with the heattransfer fluid and the cost effectiveness of adjusting the conductivityof the heat transfer fluid to the desired level for the heat transferfluid's anticipated application.

Typical antistatic fluids are ExxonMobil™ Chemical's line ofde-aromatized hydrocarbon fluids known as Exxsol™ fluids. Representativefluids and their distillation points include Exxsol™ antistatic fluidshexane (65 IBP (° C.) min, 71 DP (° C.) max, and additive amount 30ml/1000 gal), D 40 (150 IBP (° C.) min, 210 DP (° C.) max, and additiveamount 30 ml/1000 gal), D 3135 (152 IBP (° C.) min, 182 DP (° C.) max,and additive amount 10 ml/1000 gal), and D 60 (177 IBP (° C.) min, 220DP (° C.) max, and additive amount 30 ml/1000 gal). The IBP is thetemperature at which 1% of the material is distilled, and the DP is thetemperature at which 96% of the material is distilled.

Other illustrative antistatic agents are based on long-chain aliphaticamines (optionally ethoxylated) and amides, quaternary ammonium salts(e.g., behentrimonium chloride or cocamidopropyl betaine), esters ofphosphoric acid, polyethylene glycol esters, or polyols. Additionalantistatic agents include long-chain alkyl phenols, ethoxylated amines,glycerol esters, such as glycerol monostearate, amides, glycols, andfatty acids.

The quantity of antistatic additive required to adjust the conductivityof the heat transfer fluid is determined by measuring the conductivityof the heat transfer fluid as the antistatic additive is mixed in andstopping when the desired conductivity consistent with the applicationto be reached. The amount of antistatic additive mixed in will rangebetween 0.001% and 10% of the heat transfer fluid by weight, andpreferentially between 1% and 7.5% by weight, though it may be mixed inat a liquid volume of between 10 and 100,000 parts per million.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flowimprovers) may be added to the heat transfer fluid compositions of thepresent disclosure if desired. These pour point depressant may be addedto heat transfer fluid compositions of the present disclosure to lowerthe minimum temperature at which the fluid will flow or can be poured.Examples of suitable pour point depressants include polymethacrylates,polyacrylates, polyarylamides, condensation products of haloparaffinwaxes and aromatic compounds, vinyl carboxylate polymers, andterpolymers of dialkylfumarates, vinyl esters of fatty acids and allylvinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501;2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describeuseful pour point depressants and/or the preparation thereof. Suchadditives may be used in an amount of about 0.01 to 5 weight percent,preferably 0.1 to 3 weight percent, more preferably about 0.5 to 1.5weight percent.

Seal Compatibility Agents

The heat transfer fluid compositions can include at least one sealcompatibility agent. Seal compatibility agents help to swell elastomericseals by causing a chemical reaction in the fluid or physical change inthe elastomer. Suitable seal compatibility agents for heat transferfluids include organic phosphates, aromatic esters, aromatichydrocarbons, esters (butylbenzyl phthalate, for example), andpolybutenyl succinic anhydride. Such additives may be used in an amountof about 0.01 to 5 weight percent, preferably 0.1 to 3 weight percent,more preferably about 0.5 to 1.5 weight percent.

Friction Modifiers

The heat transfer fluid compositions can include at least one frictionmodifier. A friction modifier is any material or materials that canalter the coefficient of friction of a surface. Friction modifiers, alsoknown as friction reducers, or lubricity agents or oiliness agents, andother such agents that change the ability of base oils, formulated heattransfer fluid compositions, or functional fluids, to modify thecoefficient of friction of a surface may be effectively used incombination with the base oils or heat transfer fluid compositions ofthe present disclosure if desired. Friction modifiers that lower thecoefficient of friction are particularly advantageous in combinationwith the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometalliccompounds or materials, or mixtures thereof. Illustrative organometallicfriction modifiers useful in the heat transfer fluid formulations ofthis disclosure include, for example, molybdenum amine, molybdenumdiamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenumdithiophosphates, molybdenum amine complexes, molybdenum carboxylates,and the like, and mixtures thereof. Similar tungsten based compounds maybe preferable.

Other illustrative friction modifiers useful in the heat transfer fluidformulations of this disclosure include, for example, alkoxylated fattyacid esters, alkanolamides, polyol fatty acid esters, borated glycerolfatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example,polyoxyethylene stearate, fatty acid polyglycol ester, and the like.These can include polyoxypropylene stearate, polyoxybutylene stearate,polyoxyethylene isosterate, polyoxypropylene isostearate,polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric aciddiethylalkanolamide, palmic acid diethylalkanolamide, and the like.These can include oleic acid diethyalkanolamide, stearic aciddiethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylatedhydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerolmono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerolmono-stearate, and the like. These can include polyol esters,hydroxyl-containing polyol esters, and the like.

Illustrative borated glycerol fatty acid esters include, for example,borated glycerol mono-oleate, borated saturated mono-, di-, andtri-glyceride esters, borated glycerol mono-sterate, and the like. Inaddition to glycerol polyols, these can include trimethylolpropane,pentaerythritol, sorbitan, and the like. These esters can be polyolmonocarboxylate esters, polyol dicarboxylate esters, and on occasionpolyoltricarboxylate esters. Preferred can be the glycerol mono-oleates,glycerol dioleates, glycerol trioleates, glycerol monostearates,glycerol distearates, and glycerol tristearates and the correspondingglycerol monopalmitates, glycerol dipalmitates, and glyceroltripalmitates, and the respective isostearates, linoleates, and thelike. On occasion the glycerol esters can be preferred as well asmixtures containing any of these. Ethoxylated, propoxylated, butoxylatedfatty acid esters of polyols, especially using glycerol as underlyingpolyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether,myristyl ether, and the like. Alcohols, including those that have carbonnumbers from C₃ to C₅₀, can be ethoxylated, propoxylated, or butoxylatedto form the corresponding fatty alkyl ethers. The underlying alcoholportion can preferably be stearyl, myristyl, C₁₁-C₁₃ hydrocarbon, oleyl,isosteryl, and the like.

The heat transfer fluids of this disclosure exhibit desired properties,e.g., wear control, in the presence or absence of a friction modifier.

Useful concentrations of friction modifiers may range from 0.01 weightpercent to 5 weight percent, or about 0.1 weight percent to about 2.5weight percent, or about 0.1 weight percent to about 1.5 weight percent,or about 0.1 weight percent to about 1 weight percent. Concentrations ofmolybdenum-containing materials are often described in terms of Mo metalconcentration. Advantageous concentrations of Mo may range from 25 ppmto 700 ppm or more, and often with a preferred range of 50-200 ppm.Friction modifiers of all types may be used alone or in mixtures withthe materials of this disclosure. Often mixtures of two or more frictionmodifiers, or mixtures of friction modifier(s) with alternate surfaceactive material(s), are also desirable.

Extreme Pressure Agents

The heat transfer fluid compositions can include at least one extremepressure agent (EP). EP agents that are soluble in the oil includesulphur- and chlorosulphur-containing EP agents, chlorinated hydrocarbonEP agents and phosphorus EP agents. Examples of such EP agents includechlorinated wax; sulphurised olefins (such as sulphurised isobutylene),organic sulphides and polysulphides such as dibenzyldisulphide,bis-(chlorobenzyl)disulphide, dibutyl tetrasulphide, sulphurised methylester of oleic acid, sulphurised alkylphenol, sulphurised dipentene,sulphurised terpene, and sulphurised Diels-Alder adducts;phosphosulphurised hydrocarbons such as the reaction product ofphosphorus sulphide with turpentine or methyl oleate; phosphorus esterssuch as the dihydrocarbon and trihydrocarbon phosphites, e.g., dibutylphosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenylphosphite; dipentylphenyl phosphite, tridecyl phosphite, distearylphosphite and polypropylene substituted phenol phosphite; metalthiocarbamates such as zinc dioctyldithio carbamate and bariumheptylphenol diacid; amine salts of alkyl and dialkylphosphoric acids orderivatives; and mixtures thereof (as described in U.S. Pat. No.3,197,405).

The extreme pressure agents may be used in an amount of 0.01 to 5 wt %,preferably 0.01 to 1.5 wt %, more preferably 0.01 to 0.2 wt %, stillmore preferably 0.01 to 0.1 wt % (on an as-received basis) based on thetotal weight of the heat transfer fluid composition.

Nanomaterials and Nanoparticles

The heat transfer fluids can include nanomaterials and/or nanoparticles.The nanomaterials and/or nanoparticles can advantageously alter the heattransfer properties of the heat transfer fluids of this disclosure.

The heat transfer fluids of this disclosure can exhibit advantaged heattransfer performance and properties in combination with engineerednanomaterials, nanomaterials, and nanoparticles.

Engineered nanomaterials, also known as nanomaterials, are materialscomprising nanoparticles that are small-scale assemblies of atoms and/ormolecules and that are produced to have unique/novel properties that aredifferent from those of the corresponding bulk materials.

Nanoparticles are particles having one or more dimensions that are inthe size range of about 1 nm to about 100 nm (nm=nanometers). In oneaspect, a nanoparticle may be considered to act without consideration ofa surrounding interfacial layer. In another aspect, a nanoparticle maybe considered to act including the effects of an interfacial layer.

Nanomaterial and nanoparticle compositions comprise, for example,metals, (e.g. Au, Ag, Pd, Pt, Cu, Fe, combinations thereof, and thelike), non-metals (e.g. C, B, Si, O, P, N, halides, combinationsthereof, and the like), metalloids, metal alloys, intermetallics,conductors, semiconductors, insulators, electroactive materials;optically active, electro-optical, polarizing, polarizable materials;magnetic, ferromagnetic, diamagnetic, electromagnetic, non-magneticmaterials; organics, heteroatom-containing organics, organometallics;inorganics, ceramics, metal oxides (e.g. Ti oxide, Zn oxide, Ce oxides,and the like); salts, complex salts, detergent-metal salt complexes,detergent-metal carbonate complexes, overbased detergent complexes,micellar-metal salt complexes, micellar-metal carbonate complexes, andcombinations thereof; single crystal, multi-crystal, multi-crystalline,semi-crystalline, amorphous, semi-amorphous, glassy, combinationsthereof, and the like.

Nanomaterials and nanoparticles also include, for example, agglomeratedmaterials, non-agglomerated materials; hydrophobic soluble, insoluble,partially soluble materials; hydrophilic soluble, insoluble, partiallysoluble materials; fulleranes, fullerenes, functionalized derivativesthereof; carboranes, boranes, borates, boramines; boron-carbon,boron-heteraoatom, boron-metal/metalloid complexes; graphene,functionalized derivatives thereof; single-carbon-atom sheet ormulti-sheet materials, functionalized derivatives thereof, singlewalled, seamless, cylindrical carbon nanotubes, functionalizedderivatives thereof; nanotubes and functionalized derivatives thereof,containing e.g. carbon, boron, nitrides, heteroatoms, combinationsthereof, and the like; nanotubes and functionalized derivatives thereof,that are e.g. single walled, multi-walled, coaxial, rolled scroll,uncapped, end-capped, and the like; nanowires and functionalizedderivatives thereof, containing e.g. carbon, boron, nitrides,heteroatoms, combinations thereof, and the like; quantum dots comprisinge.g. semiconductors, Cd selenide, Cd telluride, and the like; molecularsheets, that are e.g. single-layered, multi-layered, inter-layered,laminated, rolled, rolled scrolled, folded, intercalated, plates,platelets, and the like; nanowires that are e.g. molecular strings,molecular wires, molecular ropes, molecular cables, coaxial cables,single and multiple wires, coiled, spiraled, interwoven, and the like;core-shell, core-coated, surface modified, surface functionalized;morphologies, in some instances, having aspect ratios that are low inall dimensions, e.g. approaching 1, and in other instances, morphologieshaving aspect ratios that are high for at least one pair of dimensions,e.g. greater than 1, greater than 5, greater than 10, greater than 50,greater than 100, greater than 500, or even greater than 1000.

Suitable nanomaterials and nanoparticles are prepared for example bysynthesis, chemical reactions, nucleation and crystal growth;crystallization, precipitation; complexation; acid-base reactions;solubilization of metal salts, metal oxides, metal carbonates;carboxylic acid-base reactions; carboxylic acid or carboxylate saltsolubilization of metal salts, metal oxides, metal carbonates;metal-carboxylate overbasing; detergent metal-carbonate overbasing;liquid deposition; physical processes of milling, grinding, pulverizing,etc. of bulk materials; colloid processes; jet extrusions, aerosoling,vaporization, vapor deposition, ion beam decomposition; physicalseparations, chemical separations; deconstruction, decomposition,digestion, delamination, intercalation, etc. of bulk materials;combinations thereof, and the like.

Incorporation of nanomaterials and nanoparticles into heat transferfluids is improved as needed by use of one or more suitablecompatibilizing agents, including for example, solvents, dispersants,detergents, overbased detergents, solubilizing agents; complexingagents, complexing agents having electron donating groups including forexample, O, S, N, P-O, heteroatom functional groups, anions, and thelike; complexing agents having electron accepting groups including forexample, metals, metalloids, B, P, Si, cations, alkali and alkalineearth ions, complex cations, and the like; micelles, micellar complexes,micellar-metal salt complexes, detergent-metal salt complexes, overbaseddetergent complexes; ionic liquids; hydrocarbyl base oils containing forexample, aromatics, heteroaromatics, heteroatoms, polar functionalgroups, polarizable groups and structures, alcohols, ethers, polyethers,esters, polyesters, carbonates, polycarbonates, amines, polyamines,amides, polyamides, ureas, carboxyl groups, carboxylates, combinationsthereof, and the like.

Heat transfer fluids containing nanomaterials and nanoparticles may haveadvantaged performances and properties including, for example, extendedservice life, improved oxidation stability, improved thermal stability,improved wear protection, improved extreme pressure wear protection,improved cleanliness, controlled friction, controlled thermalconductivity, controlled heat capacity, controlled electricalconductivity.

The nanomaterials and nanoparticles may be used in an amount of 0.01 to20 wt %, preferably 0.1 to 10 wt %, more preferably 0.5 to 7.5 wt %,still more preferably 1 to 5 wt % (on an as-received basis) based on thetotal weight of the heat transfer fluid composition.

When heat transfer fluid compositions contain one or more of theadditives discussed above, the additive(s) are blended into thecomposition in an amount sufficient for it to perform its intendedfunction. Typical amounts of such additives useful in the presentdisclosure are shown in Table 3 below.

It is noted that many of the additives are shipped from the additivemanufacturer as a concentrate, containing one or more additivestogether, with a certain amount of base oil diluents. Accordingly, theweight amounts in the Table 3 below, as well as other amounts mentionedherein, are directed to the amount of active ingredient (that is thenon-diluent portion of the ingredient). The weight percent (wt %)indicated below is based on the total weight of the heat transfer fluidcomposition.

TABLE 3 Typical Amounts of Heat transfer fluid Components ApproximateApproximate Compound wt % (Useful) wt % (Preferred) Antioxidant 0.01-5 0.1-1.5 Corrosion Inhibitor 0.01-5 0.1-2  Antifoam Agent   0-30.001-0.15

The foregoing additives are all commercially available materials. Theseadditives may be added independently but are usually precombined inpackages that can be obtained from suppliers of heat transfer fluidadditives. Additive packages with a variety of ingredients, proportionsand characteristics are available and selection of the appropriatepackage will take the requisite use of the ultimate composition intoaccount.

Embodiments Listing

The present disclosure provides, among others, the followingembodiments, each of which may be considered as optionally including anyalternate embodiments.

Clause 1. A method of operating a heat transfer system includescirculating a non-aqueous, dielectric heat transfer fluid through a heattransfer circuit in fluid communication with an electric system, theheat transfer circuit including a pump, a conduit, and a heat exchanger,obtaining real-time measurements of fluid properties of the heattransfer fluid within the heat transfer circuit, the fluid propertiesbeing selected from the group consisting of density (ρ), specific heat(c_(p)), dynamic viscosity (μ), and thermal conductivity (k),calculating a dimensional effectiveness factor for the heat transferfluid (DEF_(fluid)) based on the real-time fluid properties and for aselected pump and a selected dominant flow regime within the heattransfer circuit, calculating a dimensional effectiveness factor for areference fluid (DEF_(reference)) and for the selected pump and theselected dominant flow regime within the heat transfer circuit,determining a normalized effectiveness factor (NEF_(fluid)) of the heattransfer fluid from the following equation:

${{{NE}F_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}},$

determining a health of the heat transfer fluid based on theNEF_(fluid), wherein if the NEF_(fluid) is below a predeterminedthreshold, the health will be considered deteriorated, and wherein ifthe NEF_(fluid) is above the predetermined threshold, the health will beconsidered viable.

Clause 2: The method of Clause 1, wherein the pump is one of a positivedisplacement pump and a centrifugal pump.

Clause 3: The method of Clause 1, wherein the electric system isselected from the group consisting of an electric vehicle, on-boardpower electronics, an electric motor, a generator, a battery, arechargeable battery system, a charging station, anAC-DC/DC-AC/AC-AC/DC-DC converter, electronic equipment, a computer, aserver bank, a data center, a transformer, a power management system,electronics controlling a battery, and any combination thereof.

Clause 4: The method of Clause 3, wherein circulating the heat transferfluid further comprises directly cooling a surface of one or moreelectrical components of the electric system with the heat transferfluid.

Clause 5: The method of any of the preceding Clauses, wherein theselected dominant flow regime within the heat transfer circuit isselected from the group consisting of laminar, transitional, andturbulent.

Clause 6: The method of any of the preceding Clauses, wherein obtainingthe real-time measurements of the fluid properties comprises monitoringthe heat transfer fluid as the heat transfer fluid circulates within theheat transfer circuit with one or more sensors in communication with theheat transfer fluid, and obtaining the real-time measurements of thefluid properties with the one or more sensors.

Clause 7: The method of any of Clauses 1 through 4, wherein obtainingthe real-time measurements of the fluid properties comprises extractinga sample of the heat transfer fluid from the heat transfer circuit,analyzing the sample of the heat transfer fluid with one or moresensors.

Clause 8: The method of any of the preceding Clauses, further comprisingsending an alert to an operator of the electric device when theNEF_(fluid) falls below a predetermined threshold, and replacing atleast a portion of the heat transfer fluid.

Clause 9: The method of any of the preceding Clauses, wherein theelectric device is an autonomous vehicle, the method further comprisingsending an alert to the autonomous vehicle when the NEF_(fluid) fallsbelow a predetermined threshold, and directing the autonomous vehicle toa maintenance station to have at least a portion of the heat transferfluid replaced.

Clause 10: The method of any of the preceding Clauses, furthercomprising monitoring a temperature of the electric system, andconcluding that the electric system has a hardware issue if thetemperature exceeds a predetermined temperature limit and the health ofthe heat transfer fluid is viable.

Clause 11: The method of any of the preceding Clauses, wherein the heattransfer circuit is heat conveyance dominated.

Clause 12: The method of any of Clauses 1 through 10, wherein the heattransfer circuit is heat transfer dominated.

Clause 13: The method of any of the preceding Clauses, wherein the heattransfer fluid is a fluid selected from the group consisting of a GroupI base oil, a Group II base oil, a Group III base oil, a Group IV baseoil, and a Group V base oil.

Clause 14: The method of any of Clauses 1 through 12, wherein the heattransfer fluid is a fluid selected from the group consisting of anaromatic hydrocarbon, polyolefin, paraffin, isoparaffin, ester, ether,fluorinated fluid, nano fluid, and silicone oil.

Clause 15: The method of any of the preceding Clauses, wherein the heattransfer fluid includes one or more additives selected from the groupconsisting of an antioxidant, a corrosion inhibitor, an antifoam agent,an antiwear additive, nanomaterials, nanoparticles, and any combinationthereof.

Clause 16: The method of any of the preceding Clauses, wherein thereference fluid is at least one fluid selected from the group consistingof biphenyl 26.5%+diphenyl oxide 73.5%, siloxane (>95%, KV100 16.6 cSt),organosilicate ester (>90%, KV100 0.93 cSt), organosilicate ester (>90%,KV100 1.6 cSt), perfluoro fluid C5-C8 (KV25 2.2 cSt), and3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane(>99%).

Clause 17: The method of any of Clauses 1 through 15, wherein thereference fluid comprises the heat transfer fluid in a fresh or unusedstate.

Clause 18: A method of operating a heat transfer system that includescirculating a non-aqueous, dielectric heat transfer fluid through a heattransfer circuit in fluid communication with an electric system, theheat transfer circuit including a pump, a conduit, and a heat exchanger,obtaining real-time measurements of fluid properties of the heattransfer fluid within the heat transfer circuit, the fluid propertiesbeing selected from the group consisting of density (ρ), specific heat(c_(p)), dynamic viscosity (μ), and thermal conductivity (k),calculating a dimensional effectiveness factor for the heat transferfluid (DEF_(fluid)) based on the real-time fluid properties and for aselected pump and a selected dominant flow regime within the heattransfer circuit, calculating a dimensional effectiveness factor for areference fluid (DEF_(reference)) and for the selected pump and theselected dominant flow regime within the heat transfer circuit,determining a normalized effectiveness factor (NEF_(fluid)) of the heattransfer fluid from the following equation:

${{{NE}F_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}},$

determining a health of the heat transfer fluid based on theNEF_(fluid), wherein if the NEF_(fluid) is below a predeterminedthreshold, the health will be considered deteriorated, and wherein ifthe NEF_(fluid) is above the predetermined threshold, the health will beconsidered viable, monitoring a temperature of the electric system, anddetermining that the electric system has a hardware issue if thetemperature exceeds a predetermined temperature limit and the health ofthe heat transfer fluid is viable.

Clause 19: The method of Clause 18, wherein the pump is one of apositive displacement pump and a centrifugal pump.

Clause 20: The method of Clause 18 or Clause 19, wherein the electricsystem is selected from the group consisting of comprises an electricvehicle, on-board power electronics, an electric motor, a generator, abattery, a rechargeable battery system, a charging station, anAC-DC/DC-AC/AC-AC/DC-DC converter, electronic equipment, a computer, aserver bank, a data center, a transformer, a power management system,electronics controlling a battery, and any combination thereof.

Clause 21: The method of Clause 20, wherein circulating the heattransfer fluid further comprises directly cooling a surface of one ormore electrical components of the electric system with the heat transferfluid.

Clause 22: The method of any of Clauses 18 through 21, wherein theselected dominant flow regime within the heat transfer circuit isselected from the group consisting of laminar, transitional, andturbulent.

Clause 23: The method of any of Clauses 18 through 22, wherein obtainingthe real-time measurements of the fluid properties comprises monitoringthe heat transfer fluid as the heat transfer fluid circulates within theheat transfer circuit with one or more sensors in communication with theheat transfer fluid, and obtaining the real-time measurements of thefluid properties with the one or more sensors.

Clause 24: The method of any of Clauses 18 through 22, wherein obtainingthe real-time measurements of the fluid properties comprises extractinga sample of the heat transfer fluid from the heat transfer circuit, andanalyzing the sample of the heat transfer fluid with one or moresensors.

Clause 25: The method of any of Clauses 18 through 24, furthercomprising sending an alert to an operator of the electric device whenit is determined that the electric system has the hardware issue.

Clause 26: The method of any of Clauses 18 through 25, wherein theelectric device is an autonomous vehicle, the method further comprisingsending an alert to the autonomous vehicle when it is determined thatthe electric system has the hardware issue, and directing the autonomousvehicle to a maintenance station to have the hardware issue resolved.

Clause 27: The method of any of Clauses 18 through 26, wherein the heattransfer circuit is heat conveyance dominated.

Clause 28: The method of any of Clauses 18 through 26, wherein the heattransfer circuit is heat transfer dominated.

Clause 29: The method of any of Clauses 18 through 28, wherein the heattransfer fluid is a fluid selected from the group consisting of a GroupI base oil, a Group II base oil, a Group III base oil, a Group IV baseoil, and a Group V base oil.

Clause 30: The method of any of Clauses 18 through 28, wherein the heattransfer fluid is a fluid selected from the group consisting of anaromatic hydrocarbon, polyolefin, paraffin, isoparaffin, ester, ether,fluorinated fluid, nano fluid, and silicone oil.

Clause 31: The method of any of Clauses 18 through 30, wherein the heattransfer fluid includes one or more additives selected from the groupconsisting of an antioxidant, a corrosion inhibitor, an antifoam agent,an antiwear additive, nanomaterials, nanoparticles, and any combinationthereof.

Clause 32: The method of any of Clauses 18 through 31, wherein thereference fluid is at least one fluid selected from the group consistingof biphenyl 26.5%+diphenyl oxide 73.5%, siloxane (>95%, KV100 16.6 cSt),organosilicate ester (>90%, KV100 0.93 cSt), organosilicate ester (>90%,KV100 1.6 cSt), perfluoro fluid C5-C8 (KV25 2.2 cSt), and3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane(>99%).

Clause 33: The method of any of Clauses 18 through 31, wherein thereference fluid comprises the heat transfer fluid in a fresh or unusedstate.

All patents and patent applications, test procedures (such as ASTMmethods, UL methods, and the like), and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this disclosure and for all jurisdictions in whichsuch incorporation is permitted.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.While the illustrative embodiments of the disclosure have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of thedisclosure. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present disclosure,including all features which would be treated as equivalents thereof bythose skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference tonumerous embodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. A method of operating a heat transfer system includes circulating anon-aqueous, dielectric heat transfer fluid through a heat transfercircuit in fluid communication with an electric system, the heattransfer circuit including a pump, a conduit, and a heat exchanger,obtaining real-time measurements of fluid properties of the heattransfer fluid within the heat transfer circuit, the fluid propertiesbeing selected from the group consisting of density (ρ), specific heat(c_(p)), dynamic viscosity (μ), and thermal conductivity (k),calculating a dimensional effectiveness factor for the heat transferfluid (DEF_(fluid)) based on the real-time fluid properties and for aselected pump and a selected dominant flow regime within the heattransfer circuit, calculating a dimensional effectiveness factor for areference fluid (DEF_(reference)) and for the selected pump and theselected dominant flow regime within the heat transfer circuit,determining a normalized effectiveness factor (NEF_(fluid)) of the heattransfer fluid from the following equation:${{{NE}F_{fluid}} = \frac{DEF_{fluid}}{DEF_{reference}}},$ determining ahealth of the heat transfer fluid based on the NEF_(fluid), wherein ifthe NEF_(fluid) is below a predetermined threshold, the health will beconsidered deteriorated, and wherein if the NEF_(fluid) is above thepredetermined threshold, the health will be considered viable.
 2. Themethod of claim 1, wherein the pump is one of a positive displacementpump and a centrifugal pump.
 3. The method of claim 1, wherein theelectric system is selected from the group consisting of an electricvehicle, on-board power electronics, an electric motor, a generator, abattery, a rechargeable battery system, a charging station, anAC-DC/DC-AC/AC-AC/DC-DC converter, electronic equipment, a computer, aserver bank, a data center, a transformer, a power management system,electronics controlling a battery, and any combination thereof.
 4. Themethod of claim 3, wherein circulating the heat transfer fluid furthercomprises directly cooling a surface of one or more electricalcomponents of the electric system with the heat transfer fluid.
 5. Themethod of claim 1, wherein the selected dominant flow regime within theheat transfer circuit is selected from the group consisting of laminar,transitional, and turbulent.
 6. The method of claim 1, wherein obtainingthe real-time measurements of the fluid properties comprises monitoringthe heat transfer fluid as the heat transfer fluid circulates within theheat transfer circuit with one or more sensors in communication with theheat transfer fluid, and obtaining the real-time measurements of thefluid properties with the one or more sensors.
 7. The method of claim 1,wherein obtaining the real-time measurements of the fluid propertiescomprises extracting a sample of the heat transfer fluid from the heattransfer circuit, analyzing the sample of the heat transfer fluid withone or more sensors.
 8. The method of claim 1, further comprisingsending an alert to an operator of the electric device when theNEF_(fluid) falls below a predetermined threshold, and replacing atleast a portion of the heat transfer fluid.
 9. The method of claim 1,wherein wherein the electric device is an autonomous vehicle, the methodfurther comprising sending an alert to the autonomous vehicle when theNEF_(fluid) falls below a predetermined threshold, and directing theautonomous vehicle to a maintenance station to have at least a portionof the heat transfer fluid replaced.
 10. The method of claim 1, furthercomprising monitoring a temperature of the electric system, andconcluding that the electric system has a hardware issue if thetemperature exceeds a predetermined temperature limit and the health ofthe heat transfer fluid is viable.
 11. The method of claim 1, whereinthe heat transfer circuit is heat conveyance dominated.
 12. The methodof claim 1, wherein the heat transfer circuit is heat transferdominated.
 13. The method of claim 1, wherein the heat transfer fluid isa fluid selected from the group consisting of a Group I base oil, aGroup II base oil, a Group III base oil, a Group IV base oil, and aGroup V base oil.
 14. The method of claim 1, wherein the heat transferfluid is a fluid selected from the group consisting of an aromatichydrocarbon, polyolefin, paraffin, isoparaffin, ester, ether,fluorinated fluid, nano fluid, and silicone oil.
 15. The method of claim1, wherein the heat transfer fluid includes one or more additivesselected from the group consisting of an antioxidant, a corrosioninhibitor, an antifoam agent, an antiwear additive, nanomaterials,nanoparticles, and any combination thereof.
 16. The method of claim 1,wherein the reference fluid is at least one fluid selected from thegroup consisting of biphenyl 26.5%+diphenyl oxide 73.5%, siloxane (>95%,KV100 16.6 cSt), organosilicate ester (>90%, KV100 0.93 cSt),organosilicate ester (>90%, KV100 1.6 cSt), perfluoro fluid C5-C8 (KV252.2 cSt), and3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane(>99%).
 17. The method of claim 1, wherein the reference fluid comprisesthe heat transfer fluid in a fresh or unused state. 18.-33. (canceled)